Sounds like it's general enough you could remove the serial numbers outright and only people who'd know the context figure it out. Still, it's fanfiction, derivative work, should be fine. I've heard tales of Disney cracking down on Japanese Kingdom Hearts fanworks, but Square seems to be much more lenient than that. Even the whole thing with Perform isn't so much their own copyrights, but 3rd parties', which have nothing to do with what you have in mind.