A good idea!
For what its worth, though, remember that "big, giant robots" are a product of the late 1950s and 1960s - they were not part of Japanese culture during WW2, and I strongly suspect that a Weird War 2 Japan experience, while it might involve "power armor" of sorts due to the Samurai connection, would probably have nothing to do with "mechs", or other Anime inspired creations.
-Doc