Button up Tank
 

I just can't seem to find if I can button up my tanks or not. What I mean is having the commander on top go inside to close the hatch so that he's not vulnerable to small arms fire.

No, you cant make him go inside. The only way to even remotely do this is to put only 4 people in the tank so that he will pop up to shoot when he needs to and go back inside when noone is firing at the tank....even then it is sorta fishy.