I think this would be a lot better if Remus kept on liking girls even after he turned into one. Residual magic or something. He could seduce Lily away from James, then perhaps Sirius would discover that he was actually born an iguana and his parents put a spell on him at birth, and we're back to Ranma 1/2 crossovers.
"Oh my fucking God, now I'm going to have to deal with being a monster twice a month!"
-- mipeltaja (imitating arghgirlnow!Remus)