There is the matter of the Dreaming Celestial, the Eternals, Xternals, and all that zaniness they could eventually work in now that the MCU is merged/going to merge. Which, by the way, sets up for a Logan reboot because in the Ultimates universe he's the first mutant. Actually, in 616 continuity, the first mutant is Selene (really an Xternal, but still first mutant) and there's a lovely kettle of fish there too...