I finally saw the movie and was inspired to build (big surprise) the mech. It does fit a fig, as seen here.
Anyone who has not seen it yet, here is the trailer. A few shots of the mech can be seen near the end.
Also, the stickers used to simulate damage and alien script are cut from actual LEGO stickers. I never cut or modify pieces (except once for a mini-fig), but I love hackin’ up the stickers…;-)