OK, let me try to be more clear. You know how when you were in a Higgins Boat landing craft in BF1942, you could hold your down key to lower the hatch, and your up key to raise it - or the other way around? I'm envisioning this for the hatches over the AT-STs' two cockpit viewports, as well as for other tank hatches.

Implement an interior for the walker and make it so that when you're inside, you actually see out through the view port, with the enemy being able to shoot you when the hatch is open. When it's closed, you've got to rely on I don't know what. I seem to remember that GC had this monitor (really just a transparent image that let you see out of the walker) set in the cockpit between the two hatches, so that when you were in seat one, you had the hatch and that 'computer image of the battlefield'. I just Googled for a screenshot on that, but couldn't find any. Or you could come up with some other way to give the player a limited view of what's outside.