The big concern I’m getting here is that if we substantially change canon in this scene, we’re going to alienate people who liked the previous canon, or at least alienate people who believe that the established canon is inevitable going forward and can’t be changed.
On the other hand, many of these changes, such as Palpatine creating Anakin to be his heir, explain so much about these sequels that it seems a shame to discard them. Similarly, Rey Palpatine is so destructive to credulity that it seems a shame to keep it as an undisputed fact.
So here’s a thought: We could move both of these changes into the realm of the speculative.
Jedi seem to have questionable visions during their training. Padme dying in childbirth in a different way than how it happened, Luke becoming Vader or seeing his friends suffer and die, Rey’s visions here. It seems like a rite of passage for a Jedi to get visions whose only purpose is to seemingly confirm their deepest fear, a fear that will only come true if they give in to it.
A big blank spot here is Kylo’s visions. What did he see during his training with Luke that made him become Kylo Ren? And here is where we can reveal this crucial part of his past: He had a vision that his grandfather was created by Palpatine, and thus his family wasn’t truly Skywalker, but Palpatine. This is close enough to canon that it is reasonable, but different enough to poison his entire worldview…and Luke’s.
When Rey has her visions, Kylo can tell her that her vision is similar to his, and it confirms that she was created by Palpatine just like his grandfather. Kylo takes her visions seriously, incorporating them into his story about their common destiny as Palpatines.
When Rey goes to Luke he tells her about Leia’s training, and the visions she had that caused her to turn away from her Jedi path. He says he suspects now that these visions happen to everyone training to be a Jedi, and while they reveal emotional truth, they may not accurately reflect reality. “Our view of the future is ever changing…but I never considered that this is also true of the past.”