The second was building it around a Plot Point setting instead of having it be a sandbox for playing mutant animals. I also wanted to keep it in modern times, as opposed to going straight to post-apocalyptic AtB. Initially I figured on going with the escaped animals trope a-la "The Plague Dogs", or maybe working for a PMC (Private Military Contractor) tentatively titled, "Dogs of War". Neither of these really worked for me.
That's where this articles title come in, "Fur and Brimstone". A couple nights ago the image of a mutant alley cat fighting a winged demon popped into my head. Then I remembered that animals are supposed to be sensitive to the paranormal, and I figured that I had a pretty good idea for a campaign: Supernatural beings are infiltrating the world, the human hunters have been nearly wiped out, and humanities last chance rests on a handful of Mutant Animal Demon Hunters. (or something like that)
I want the mutant animal creation system to be able to stand on its own so anyone can play what they want, but I also want there to be some sort of skeleton to support it like the TMNT comics supported the original TMNTaOS RPG.
Once I have more, I'll see about posting it.