One person fills all rolls on the plane and the GV,, gunners die, that position is lost in both planes and GVs, the turret gets knocked out,maybe the gunner is dead, rear plane gunner is dead,same thing.
The commander veiw is relatively new, we used to have a drivers position instead of the commanders position, this makes more sense than that did tho I loved the old way and would love to have all positions back,, if we did, I could see killing the commander and controlling the tank from the gunner or driver position but that's not possible today.