Mechs are fine in the comics and might even be fun to experiment with in video games, but I think they're a little too cartoony for the films themselves.
Personally, I wouldn't mind a glimpse of a very large colony, or an Earth city. The film doesn't have to be set there, but I'd be interested to see what a major metropolis looks like in this universe. That itself would have room for all sorts of technologies, particularly in terms of travel.