Red Orchestra 2 has an excellent solution where you be alone or use all positions, manned or not.
Individual crewmember can die, and you can move surviving crew into different positions within the tank.
Commander can stay unbuttoned or in cupola- looking through periscopes. you can also drive the tank from gunnners position and from commander position.
you will see less main-gunning down planes, since you need to jump to gunners small optics view, if you are not lucky to have enemy plane already in sight there.
Repair should take place at rear areas, or take you chance being gunned down while repairing the tank.