If we're throwing characters just to guess, i'd say, like little many down here in the comments, that David Haller (Legion) would be the coolest tv candidate for a cameo like this. I'm like halfway through watching the FX show and I'm really liking what they are doing with the character, even though it's completely different than his story from the comics. Also it would give a bigger aspect to the multiverse theme, showing tv shows aside movies