Here's an interesting theory on how to bring the X-Men and Fantastic Four into the MCU
Since the announcement of the merger between Disney and 21st Century Fox, people have wondered how, exactly, all of these disparate comic book characters would finally be brought together. For years, Marvel superheroes like the X-Men and the Fantastic Four have been sequestered to separate franchises, timelines, and universes because different companies had control of the property rights. But, no longer! Still, the question remains, how the hell are Disney and Marvel going to bring these wayward heroes back into the fold? Well, as Esquire points out, at least one fan out there has a pretty decent theory that ties in with the upcoming sequel to Avengers: Infinity War.
At this point, everyone is aware of the universe-shattering event that ended the first part of Infinity War, and it can pretty much be assumed that the follow-up movie will be all about reversing said event and bringing back all our heroes that got dusted. Reddit user PhobetorWorse thinks this reversal—which a lot of people think will involve either Captain Marvel wielding the infinity stones or a few of the original Avengers sacrificing themselves—could be the event that gives the Fantastic Four their powers.
All of this brings people that are not on Earth, back as well. Meaning the F4 are introduced as scientists exploring the negative zone and ripped back to Earth forcefully through the Negative Zone (Reed and Sue theorized that humans could have randomly been “switched” to this zone like the real-life phase change) barrier—giving them abilities.
This is seen as the ultimate insult by a former colleague of Richards’. He was also in an accident that forever changed him, and instead of praise, his human rights violations came to light and he was forever thrown into darkness. That’s right baby, Mole Man is the villain this time. He brings to light an accident that Reed had “caused” as graduate student. This revelation paints doubt over his incredible abilities and instead neglect (Doom was the injured party. SEQUEL SET UP).