Yeah, you "lead" with your eyes... unless you're daydreaming or such, your eyes are always focused on something. If you look around 360 degrees, your eyes won't do the motion linear, they'll skip between details.
The thing with motionblur in games (the camera movement dependant one) is that you forget the fact that the player's eyes are already focusing on different areas of the screen... when you look around quickly in the game, you're already missing details, just like in real life. I.e, the motion blur is simulating something that is already taking place. Unless they're aiming for pure eye candy, of course. ;)
Anyway, back on topic. I agree that it's really frustrating playing the commander in an M1A1 or LAV-25, but if it's done like that because those vehicles doesn't have a stabilized independent viewport for the commander then so be it in my opinion.
I'd be more interested in being able to tell the (AI) gunner to look in directions relative to the tank or something like that. There's already the Alt key Look At command, of course, but it'd be nice to get the gunner to relax a bit.
It took me a while to figure what key switched to the "periscope" for the LAV-25, btw.