I agree. You want more punch? Equip the machine gun. Want accuracy? Use the sniper rifle. Magazine? Perhaps that would be clip differences. Have more than one clip available for use for a gun, like the grenade launcher. Some clips take more room and more TU to change clips, but hold more rounds, other clips are smaller, carry less, take less room, and dont take long to change.
Maybe its not the equipment that needs to change, just what goes into it. Model some clips, and see what people say