Thanks for the response. I'd be happy to volunteer for any of the following cannon characters, roughly in order of preference:
Charles Xavier (though you might prefer to keep him an NPC, I would love to play him)
Hank McCoy (presumably the furry blue model, but the original version would be okay too; he had a long term relationship with Vera that ended badly, perhaps when he changed forms, and would be what, about 31 now?)
Doug Ramsey (didn't die on schedule, about the same age as Kitty, maybe a year older)
Sebastian Shaw, head of the Hellfire Club, looking to protect mutants from the Sentinels and other threats but not looking to bring on World War III. If you want to leave Sebastian as an NPC, then perhaps another Hellfire Club male such as Harry Leland (who would have survived the fight with Pierce).
While I have a concept for an original, I'll keep that for when those ideas are sought.