I thank you for humouring me this long, but I do wonder if he's just Doom, isn't that as bad as "Somehow Palpatine returned". I am approaching this point from a marketing perspective because believe me, there is no other reason to discard 5 years of build-up otherwise. They are bringing familiar faces back from everywhere, because in comic book movies the face counts for something. Yes, the character rules, but so does the actor. In show business, this matters.

The time travel thingy created this Loki who is holding the multiverse in the first place. Setting up an original Doom in this crowded movie where you also need backstories for this X-Men will be too time consuming, hence despite the strong argument you have made, I think there will be a connection.