I have a suggestion, about two guns.
Snipers
A sniper would be a very good edition to the game, then you could actually make a sniper tower and actually snipe in it. A sniper would add a whole new way to play the game, and we could all try to pull off some 360 noscopes! The sniper should probably be at least a three or four shot kill, when not shooting in the head, a headshot is obviously a one shot kill.
Handguns
No matter what gun class you chose, you would always get a handgun with it. Handguns aren't that powerful, but can be useful when you are in the heat of battle, and you run out of ammo on your main gun.
Medic Packs
I think that the game should randomly place medic packs anywhere in the map at any random time. A medic pack could restore about 50 health. This would be very useful when you are far away from your team's side, and could at times save your life. You could just walk up to it and heal yourself.
Health Regeneration
This could be kinda cool. Basically, the idea is, you regenerated health very slowly, oh, about 1 point of health every second or two, but it would be kind of neat. If there would ever be medic packs though, this wouldn't really be needed.
Throwing Knives
If you wanted to, you could substitute three grenades for one or two throwing knives. If you hit somebody with one, it would be instant death. I think this would be pretty cool
Those are some of my ideas, hope you like them! :]