Well, my concern here remains that we will apply ridiculously higher tiers than what any current writers and editors actually intend to these characters.
For example, Odinforce Thor explicitly defeated the Black Winter, a multiverse-consuming entity, recently, and he and three avatars of the Phoenix Force together prevented the corpse of the First Firmament from destroying the entire current Marvel multiverse through an act of raw power a few weeks ago (Avengers Assemble: Omega), and plenty of other characters consistently scale to them, and even more to them.
Jonathan Hickman portrayed the Marvel multiverse as strictly being a collection of universes that were colliding into and destroying each other, and I do not think that Al Ewing ever remotely mentioned infinite degrees of infinity or enormously higher in his cosmology.
So if we revise the Marvel multiverse as a whole to tier 0, as Ultima likely intends, as it is the standard pattern I have noticed from him in these types of situations, we will also end up with tier 0 regular powerful superheroes, which I think even most of the more extremely dedicated and upgrade-hungry at any cost fans of this franchise will consider absolutely ridiculously unreliable.
As such, I still think that it seems much more reliable to at least split the scale of the cosmology into the classic era that Mark Gruenwald, Tom DeFalco, Roger Stern, and other writers defined, and the modern era mainly defined by Al Ewing and Jonathan Hickman, and possibly another split for J.M. DeMatteis as well, and to only use explicit and consistent statements regarding the intended scale of the franchise.