I think, but am not sure, that Hite's version of this idea is also to be found in
GURPS Infinite Worlds: Lost Worlds, as the Nine Worlds skerry. Each world is some variation on WW2, either an alternate version of real history or a very odd world that echoes the themes of WW2.
As for other ideas, I'd look at using Ratatosk as a guide for the PCs at some point. Alfheim as a world plagued with UFO aliens like the Greys and the Nordics (i.e., "ultraterrestrials" which have a lot of commonalities with Fae mythology) would be cool. Having a 1950s UFO setting ties in nicely with Monster island kaiju, too.