I've been torn with this idea for a while, in one way I'd like to see more realism being that if a commander is in a commanders view he's using binoculars to view outside the tank, for any reason he's strafed and killed you are stuck in the gunners position.
That being said I have to go back to balancing the arcade and realism for the sake of making things enjoyable and the learning curve not so steep to new players, however just like real commanders of tanks - if you are in a "green area" then you can unbutton and view with binoculars, however in a hot zone - you'd be lucky we don't have the million other things that killed tank commanders that were unbuttoned (snipers, mortars for example).
To make it simple - if you are in a commanders position and get strafed, you have the chance of having him killed, if you are in the gunners position you'd be buttoned up.
Just more fuel for thoughts, +1 on the idea, its a VERY good idea.