I think a BMF Sandcrawler is not...too out of the question. It's a very good playset, and features heavily in the Lego Star Wars game, so it has a chance.
Too bad they didn't do that during build a droid, and you could set up inside.
Who knows, maybe they will take adavantage of all the BAD parts, and use them as pack in stuff.
It could also have some sort of hidden gun, or winch, or crane or something, for play value. Plus lots of hatches and stairs and play spaces. It could even have some sort of Mini-Rig that rolls out like the BMF's life pod thingy. The more I think about it, the more I think it could be super cool.