I find that the smg has its uses and it should be kept in the game but the addition of an assault rifle would add extra challenge to riflemen. Basically an assault Rifle would have these features...

-Burst or single fire
-less accurate than semi rifle but alot better accuracy than smg
-much slower rate of fire than Smg
-Same or slightly less damage as rifle

This would provide a good competitor to the rifle and general assault weapon but still not replace it just make the rifle a choice for snipers.
while smg users would have to put it to use as a stealth weapon.

I like this idea, an assault rifle that fired in 3-round bursts/fully automatic (but with a much slower rate of fire than that of the SMG) that has lowered accuracy but the power of a rifle round. As a matter of fact, the assault rifle could have the current accuracy of the standard rifle (with the cone spread) while the standard rifle can be set back to its original pin-point accuracy.

The assault rifle seems like a nice stopgap between the SMG and the standard rifle while remaining balanced. This would also remove the need for my previous suggestions of a light/medium machine gun.

(I personally would have liked a fully-automatic assault rifle to be implemented instead of the SMG, but what's done is done.)

No. I like the simplicity of the weapons systems, all weapons should have a unique functions, like the rifle is a single shot weapon, the SMG is a rapid fire weapon. We need unique weapons like a Shotgun that fires multiple bullets or a Flame thrower that toast blocks and creates Barriers of Fire.

@Camelsaurus: I agree. Besides, with the current accuracy of the SMG it's almost as good as the rifle. I use it as I would a carbine a lot of the time, and it works pretty well.

flame throwers are not simple Camelsaurus , a selection of normal guns such as different variations of an automatic and semi-auto gun would provdide a great sense of balance with certain guns having advantages over others in different situations e.g high powered semi rifle is good to snipe with while a semi auto pistol would be good at extreme close range. Assault rifles on the other hand would provide the general all rounder in terms of fire power.

Flame throwers are simple as long as they're more like fire hoses where it sprays napalm instead of breathing fire. And Unique Guns only shortens play-throughs and weapon testing for users, they won't have to decide between two rapid-fire guns for instance.