As far as I'm aware only the 16 player would be considered a Walker free zone, and even that is still open to discussion. The problem with a Hoth map, is that people are going to expect Walkers in there, to get the full experience. The way I see it personaly is that all the sizes of Hoth map should feature Walkers and the Rebel Base as that is what the map is there to depict, what should change with the map sizes are the number of Walkers in play and the portion of Echo Base (restricted areas for 16 & 32, and the full base for 64) that you get to play in.
Having two maps for the exterior and interior battles of Hoth is a possible option, but we'd want to look at trying to encompass it all in one map before we'd turn to that, and as the beta and test builds since have shown we have ample room in the available map space to do the exterior and interior battles on Hoth justice in one map, it is just a case of how the map fares with optimisation once we have all the fully detailed assets on there.
We'll keep you all informed with interesting updates on our progress with this in the future.