I get your point, "commander" sitting there looks cool and all, but he is nothing more than a trouble for the real commander (driver) of the tank, making it harder for him to use the free look cam, which is usually placed on the commander cupola's hatch. Player sitting there is no advantage for you, because he's not even able to do the 360 degree spotting like you can by pressing [ctrl] button while driving, what makes him even less useful than your hull gunner who can not only spot for you but also shoot the enemy infantry. Shooting a hand weapon from the cupola of the moving tank is nowhere near as effective. And I wouldn't ever rely on anyone to be my eyes on the battlefield anyway, I would rather see that extra player to be me infantry support on the battlefield, or an actual spotted with binocs, somewhere else, giving me coordinates of far away targets.