[PlasmaKrab]

I have no reports on actual infantry actually firing from IFV gun ports in actual combat, but anyway I think that this would occur only in rare circumstances, and most of these (fighting off close-in infantry, assaulting on the move, etc.) would rather require the grunts to stand and fire from the hatches (as the Swedish apparently do on the CV90 and previously on the Pbv302, among others), which could possibly be modelled as well, this time accounting for some vulnerability of the squad.
Thinking aobut it, I wonder if that standing-out-of-the-hatch-with-weapon-pointed is much more than a show of proficiency or at most something you use on patrol, out of actual enemy contact? Then the sighting of an enemy, either from the squad or the crew, would call for the infantry to dismount at once to dig in and not be toasted with their APC in one (un)lucky shot.