i think xavier making the entire planet "forget" to protect mutants is a great solution because
1) it's some old school xavier dickery that isn't completely out of character
2) it solves the "world is more tolerant now, and in the mcu, heroes are beloved celebs, so why would they hate mutants?" problem. because it would be good reason to hate mutants when you find out their leader mind-wiped you. it'd be a nice little cruel irony of life, where xavier's greatest fear is realized due to his own actions to protect his kind
either way, i still would want them to recast everybody except stewart as xavier, just because i'm selfish and want to see just ONE illuminati scene with him, rdj, cumberbatch, boseman, etc
I actually proposed this a while back. Some where opposed to the idea, but I think this is the perhaps one of the only solutions that makes the most sense. It does, in fact, coincide with established Lore, which Xavier has done in the comics.
Also, it helps to immediately establish just how powerful Xavier's mental abilities are. Finally, it gives us more world building. It fleshes out this world with more of a dark undercurrent than we were initially lead to believe.
For Example: Back during WWII, the Mutant Gene began manifesting itself. Erskine began testing his Super Soldier serum to combat Hydra. However, certain facets of the Government wanted to use the Super Soldiers to combat the potential Mutant Threat. With Erskine dead this put that project on hold. Rob, over at Comics Explained made an excellent suggestion that these factions within the government had another name for the Super Soldier Project: Weapon I (1).....I think you can see where this is going immediately.
As Mutants started to become more prominent, Shield began to intercept them. They were approached by Professor Charles Xavier, who became a Consultant/Liaison between the Mutants and the Government, helping to bridge the gap. Nevertheless Anti-Mutant sentiment began to grow. Panic, fear and mistrust deemed that the Mutants were just way too dangerous. Xavier offered to train them, and help them but his offer was refused.
Xavier then uses his abilities to wipe Mutants, and the very history of Mutants from the minds of humanity in order to protect them. Our entry into this is Vision. Even if he doesn't make it out of Infinity War or the sequel, he if the character that uncovers the truth. At some point between the events of Civil War and Infinity War, the Mind Stone reveals that memories have been erased, or are missing. As he learns to use the Mind Stone it leads him to Charles Xavier.
What's critical is that Vision himself said in Civil War that: "...ecalation leads to conflict,.....and conflict leads to catastrophe." Once Xavier explains what occurred, Vision allows him to remain in secret. The only question is: What threat would cause the Mutants to come out of hiding ?
Having the Mutants come from a different reality or Earth is stupid, when established Lore is staring us in the face.