I was thinking of removing the collision mesh from the feet to see if that will make it easier to place on a map.   I was also looking at possible adding some invisible wheels to the feet to see if that would allow the feet to touch ground without bouncing.

Even as multiplayer only,  the ATATs need a gameplay weakness since trying to use tow cables deployed from snowspeeders would be too difficult for First Strike.    Maybe add some missles to the snowspeeeders?

The game engine has physics problems with very large walkers.

The big problem is that they are very unstable and bounce if they hit the slightest bump. 

They also have a hard time climbing up hills.

I was able to set them up with autopilots but keeping them on track was a huge problem. 

So mobile AT-ATs are really out of the question unless someone can figure out how to make it more stable.