Actually, colored smoke would not be anything new, but a visual upgrade to existing smoke grenades. And that would be pretty neat.
how about an automag? it shoots many paintballs inaccurately over a short distance, like a shotgun
Uh, shotgun would rather shoot multiple pellets AT ONCE, with spread and quite long reload time. It would rock at short range, but due to long reload, it would take some skill to use it well. Ditching Stingray or VM in favor of this would not be that bad of idea IMO.
As for sniper, how about sth even slower than pgp in ROF, but insane when it comes to base ball speed?
Hey, quick melee attack (like paintbrush/barrel tag) would be neat as well.