The only problem is finding a Tokyo-based sci-fi property that's NOT Godzilla (He's too perfect of a replacement for Disaster)
Space Fantasy as a shoot 'em up dark ride could work if there was an anime/sci-fi subland within Tokyo.
Best case scenario for a Tokyo land:
Space Fantasy replaces MIB as the anchor of a anime subland
Hello Kitty gets a boutique and carousel along the Universal waterfront
Pokemon gets a mini-land where Fear Factor is (interactive Pokemon battle show along with Springfield-esque recreations of the Pokemon Center, Pokemart, and the Saffron City skyline)
Fast and Furious takes 80-85% of the MIB/Springfield plot
Godzilla replaces Disaster
We all live happily ever after