I think it'd be fun to see sort of a reversal of the classic premise: have a team of characters from different realities become temporarily stranded in the 616 -- see how characters from the 2099 or MC2 or any other world thinks about Krakoa.
In fact, if it were up to me, I'd have a team of characters suddenly appear along with a Phoenix Egg, claiming to have escaped from some evil mutants, and then moments later have THAT team show up with a Phoenix Egg, claiming the same thing.
Lots of room for all kinds of different alt-universe characters.
-Pav, who would have to bring back Brimstone Love...