well, slightly innacurate mortars would make good infantry battles.
and engineers that lay mines will make the player have a few spare engineers layin around so he can quickly mine up a road. maybe mines can be 1 ammo bar, and it reloads after 30 seconds? so that way an engineer has infinite mines, but takes a bit.
ehh... infantry cant get in buildings? or you mean deploy in buildings? (im being dumb right now)