There seem to be three different sub-types of players. Those who like to build elaborate bunkers, those who like to dig a little hole and snipe, and those who say eff it and rush at the other two. I'd like to propose three classes and a few weapons that should make each camp more powerful at their preferred job, but more reliant on other players to cover their weakness.

Here is a rough outline, with items listed by keybind.

DEFENSIVE CLASS: Gunner

Oriented toward bunker building and controlling terrain with his machine gun, his lack of grenades and reliance on a pistol when his gun isn't deployed means he is very weak when unprepared and needs teammates to defend his position's blind spots. His concrete is pick-resistant, grenade and shovel-proof but limited to base resupply, while his belt-fed machine gun can overheat but never runs out of ammo.

1. Shovel
2. Pick
3. Blocks (x50)
4. Machine Gun
5. Pistol
6. Concrete (x25)

MIDFIELD CLASS: Grunt

The current class plus, the Grunt is always capable at offense or defense, but at his best when supporting a specialist or attacking specialists from their weaknesses. He can heal teammates, but not himself, with the bandage, encouraging riflemen to buddy up to better survive. His camo blocks can be assigned any color as a regular block can, but consist of mostly empty space with just enough colored voxels to break up outlines, allowing him to conceal his face behind it and snipe at unattentive enemies.

1. Shovel
2. Pick
3. Blocks (x50)
4. Rifle
5. Grenades (x4)
6. Camo (x25)
7. Bandage

OFFENSIVE CLASS: Assaulter

Slightly faster than the other two classes, the Assaulter sacrifices building ability and range for close-in firepower. Unable to dig, his limited supply of blocks, unable to be refilled in the field, are only intended for negotiating obstacles. However he enjoys the only mobile automatic weapon in the game, the somewhat inaccurate submachine gun, and the only concrete-busting explosive, dynamite. With these tools he is equipped to blast and shoot his way through machine-gun nests and trenches. However when stealth is preferred, the knife allows him to run silently at his slightly-faster speed and catch intel-guarding sentries unaware.

2. Knife
3. Blocks (x10)
4. Submachine Gun
5. Grenades (x2)
6. Dynamite (x2)

For a rough pattern I am looking at the Korean War, which featured a lot of hills and mountains, a lot of infantry brawling, and a LOT of trenches. There were three basic small arms used there; semi-automatic rifles, submachine guns, and machine guns. Everyone is pretty familiar with these from the volume of WWII games out there, but I'll be clear; powerful machine-gun positions (and doubley so artillery) force trench fighting. So I will start with the machine-gun and its class, the Gunner.

DEFENSIVE CLASS: Gunner

Currently most defenders can get sniped out of their elaborate multi-story bunkers without a need to close for hand grenades, leaving just a hollow box to ignore and avoid. With machine guns, the volume of fire allows you to win a plinking fight, but even this won't be good enough of itself. After all, if you get sniped in the head on the first shot, your machine gun dies as well. This gets rid of the incentive to watch out a window all day, since the enemy will spot you first and empty your helmet. Instead a machine-gunner might take the gun and pull a John Rambo, which is great and all, but now we've nothing but a newly overpowered offensive class.

The solution is a deployable machine gun with a steel shield. Deployed like a block of voxel terrain, the tile occupied by the gun -cannot- be shot through, ever, and can only be destroyed by the pick (returning the weapon to its deployer) or explosives. Helping the gunner build a strong nest are his limited supply of concrete blocks, renewable at the base or slowly salvaged with his pick. With a bunker of his design the gunner can command everything the deployed gun sees outside of his window. With an interact key he can enter and leave the gun if threatened, and even let another trooper take over while he heads back for more concrete. Or if he decides to pack up and move, his pick quickly dismantles the gun back into his inventory and he can head for greener pastures.

The machine-gun itself shoots rifle powered rounds at a steady rate of fire and near-rifle accuracy, allowing the gunner to quickly kill exposed troops but not quite give him a bullet-proof sniper's scope. Enemies occupying a trench with a machine-gun firing on it will be strongly encouraged to keep their heads down by the constant drumming of potential headshots whistling overhead. The gun itself doesn't run out of ammunition, but a heat bar will slowly build up. Once full the gun cannot be fired until it has completely cooled again. For a Gunner operating the weapon, he has the option to change the barrel with R, which plays a short sound and quickly returns the weapon to action. For other players borrowing the weapon, no such option exists. This reduces the usefulness of a borrowed MG and encourages but does not force Gunners to man their own positions. If a gunner is shot, his old gun remains in place and he is able to place a new weapon. However if he places a third gun, his first will despawn. This prevents MG's from cluttering the field but still lets gunners have two guns to play with.

Naturally his pistol is a dismal eight-round weapon, fairly inaccurate, and unable to instantly kill with a headshot. Its only saving grace is a slightly faster-firing semi-automatic mode and low recoil. With clever murder-holes inside his bunker he stands a fair chance at defending himself from a single rifleman, but generally will need other troops around to protect him from close combat.

Concrete is just what it sounds like; semi-permanent building blocks. It can be destroyed with a pick after about five seconds of frantic chipping or blown up with dynamite if you happen to have it, but otherwise provides grenade-proof, shovel-proof, bullet-proof protection for the industrious Gunner. Large blockhouses can form near the base to improve defensive play, while simple concrete walls or pillboxes grow as midfield positions prove their value. Each concrete block is a mix of a few shades of grey, making them possible to spot from ordinary grey blocks. Gunners are encouraged to use economy when placing concrete due to its requisite return to the base when the twenty-five blocks are exhausted, compared to dirt which is easily collected with the pick.

Is it balanced? The gunner can dominate large areas of the map, but only one window at a time. He can leave second guns for teammates, but said teammates will no longer be watching his back from close combat. And he has no grenades, so he has no way to reach an enemy simply standing to the side of his window chipping at his concrete with a pick or dynamiting him out. The gunner ultimately relies on riflemen to protect the outside of his bunker from being overwhelmed from the flanks. And offensively, the gunner can be of some use in a hasty position hammering at the enemy battlements, but will require other soldiers to clear and capture territory.

MIDFIELD CLASS: Grunt

There isn't much to say about the Grunt, and that probably suits these players fine. By not changing much about the current loved trooper, we avoid shaking up anyone's playstyle. However we do add two tools to his inventory, camo blocks and bandages. These strengthen what he is already good at (entrenching and sniping) and add a team benefiting skill (healing).

Grunts are as at home in a Gunner's bunker covering a secondary window as they are taking out an enemy bunker with grenades. Friendly assaulters will appreciate their shovel and pick in digging tunnels or breaking through defenses, while enemy assaulters will hate them for long-range firepower that picks them off before the SMG becomes effective. And of course two opposed pairs of Grunts can exchange curses and bullets with eachother as they exchange bandages with themselves. Grunts specialize in doing better what the other classes can't do at all, and so a Grunt player will always be a worthwhile addition to the team.

The bandage is a simple 'weapon' that quickly heals up injured soldiers. It is infinite but cannot be applied in full force to the player using it, keeping it from being a rambo tool. Instead Grunts very slowly recover health while the bandage is held in their hand. A stubborn grunt in a foxhole can take a hit and return to the fight by himself, but two grunts working together will put a lot more pressure on the enemy in much shorter time because of the effectiveness gap between self-healing and buddy-healing. This healing power lets grunts hold trenches and foxholes more effectively than before. And if a revive ability was ever considered for the game, I would recommend the Grunt have it.

Camo is another deployable block type. Unlike concrete, which obviously stops bullets, camo does not. It also does not block sight completely, having a mix of clear and colored voxels inside of the block. However it does prevent moving through itself, allowing players to build a sort of barbed wire wall that needs chopping through and doesn't provide shelter from defensive fire. Camo is destroyed by any explosive, picks, shovels, or the knife, being slightly more resistant than regular blocks for hand tools destroying it. It, like concrete, can only be placed or recovered, never collected by destroying regular blocks. Camo can be matched or assigned to any color allowing team-colored camo, concrete-colored camo, fleshtone-colored camo, or even black camo to make your 'barbed wire' a little more imposing. Camo will find its use largely in the midfield by breaking up the outline of helmets peeking out of trenches and foxholes, or be incorporated into bunker designs. Who wouldn't be proud of an enormous camoflague-covered concrete bunker guarding their intel with little machine-gun murder-holes concealed behind concrete camo blocks?

Lastly, his offensive and defensive power is boosted with four grenades, keeping him effective against his upcoming short-range rival, the Assaulter, and able to flush out Gunners from even the most elaborate casemates.

Is it balanced? By being better than the other two classes in most situations but worse than them in a few situations, Grunts should make up the bulk of teams, especially with the attractive healing ability and long-range weapon. This is ideal for everyone, I'm sure.

OFFENSIVE CLASS: Assaulter

Some people just can't stop moving. Other people aren't good with the rifle. Yet a few more just want to blow stuff up. The Assaulter is for these players. Armed with a submachine gun, dynamite, and grenades; this trooper sacrifices earthworking tools for offensive punch and a small boost to his speed as well. With Grunts providing covering fire, Assaulters storm concrete pillboxes and blast them open with dynamite, then clear out the defenders with grenades and submachinegun fire. If the assaulter comes across really well-built defenses, he may be stalled up with his lack of spade and pick if the explosives run out. In these situations, switching to the knife and trying to sneak in may be the best choice if he's cut off from the grunts. By offsetting his destructive and offensive power with a lack of range and construction tools, the Assaulter becomes a specialist just as the Gunner did, unable to replace the Grunt but far better as part of a team.

The Submachine Gun is a simple enough weapon to understand. By firing pistol-powered bullets in quick bursts, Assaulters can drop enemies at close range before a Grunt or Gunner can pull the trigger a second time. But with its recoil and inaccuracy, Assaulters have to hope to get lucky beyond medium range shooting where Grunts excel. The weapon has a twenty or thirty round magazine (balance depending) and enough ammunition to last a quick and violent assault or a slow and methodical one. Ideally an Assaulter who runs out of ammo is already returning to base with the intel.

The Knife is a specialty tool for the Assaulter. It allows him to quietly infiltrate enemy lines by removing his running sound while in hand and lets him destroy camo nets and deployed machine guns quietly, if he can sneak up on them. He does not run any faster, however, so once detected he's best off getting his gun out and shooting through.

Dynamite behaves similar to grenades with two exceptions. One, it cannot be thrown as far but has a longer fuse time. Two, it destroys blocks two spaces away (5x5) where current grenades destroy blocks one space away (3x3), and destroys concrete one space away where grenades cannot destroy concrete. This makes it ideal for big demolition jobs like destroying an enemy bridge or trench, or cracking holes in concrete bunkers to knock them out with grenades. Dynamite emits the sinister hiss of a burning fuse when thrown, giving some warning to everyone around.

Is it balanced? Unable to out-shoot a grunt or gunner at long range, but tearing through them at close range, Assaulters will never dominate the teams because they can neither hold terrain nor drastically manipulate it. Assaulters may well be stopped by terrain obstacles that Grunts could shovel through, and while they can make great use of hidden tunnels cannot dig them. Ultimately the Assault class will likely stick close to grunts and gunners, defending bunkers and trenches with their submachine guns until the call comes up to clear an enemy strongpoint with their explosives. Or, if feeling adventurous, the assaulter can try sneaking around the edges of the map to find a blind spot of the enemy's before a grunt pulls a bead on his head.

In conclusion this proposal depends on only a few new programming tricks; partially colored and partially clear terrain blocks (camo), variable durability blocks (concrete and camo), placable, interactable blocks (deployable MGs), healing tools (bandage), and variable damage explosives (dynamite). Everything else is just new voxel art, sound effects and getting players (and the developers, obviously) to accept the ideas. I hope my time as a Project Reality developer lends a little credence to my suggestion, and I'm eager to discuss it with anyone who sees a possible problem and make changes as debate determines.

I also had the idea for a mortar that tosses grenades based on bearing, elevation and power input, but maybe later.

TL;DR

Everything above is legalese nonsense promising you free beer if you post your complete agreement for the OP.