No, all your ideas suck.

We should have only 2 classes:
-Soldier
-Builder

that's it.
Also, I request sidearms... they can be really helpful

how about not a class system but a ranking one? ...... just a thought...

Soldier
-Rifle with 50 ammo
-Pick is normal
-Shovel is normal
-25 starting blocks, cap of 50
-3 grenades

Builder
-Pistol with 40 ammo
-Pick is much stronger
-Shovel is faster
-50 starting blocks, cap of 150
-1 demolition charge (powerful against blocks)

Medic
-Pistol with 15 ammo
-Pick is normal
-Shovel is normal
-No starting blocks, cap of 20
-3 healing packs (healing, durr)

Scout
-Rifle with 30 ammo
-Pick is weaker
-Shovel is slower
-20 starting blocks, cap of 30
-3 climbing ropes (can go up a straight wall of x height)
-1 radio (reveals the enemies' locations for 30 seconds)

Sniper
-Extra-accurate/damaging sniper rifle with 20 ammo
-Pick is normal
-Shovel is normal
-10 starting blocks, maximum of 10

Engineer
-Shotgun with 30 ammo
-Pick is stronger
-Shovel is faster
-40 starting blocks, maximum of 80
-3 layable mines

I have mixed feelings. IMO it's either basic classes or more weapons to choose from

I would say NO for classes, BUT a possibility to change the weapons with the 1 class what we have would be nice, so your enemy doesnt have all the guns at the same time.