MCU Mutants as a new rising phenomenon, and us the audience watching the new age of mutants slowly rise up would be a fascinating way for them to bring the X-Men into a Marvel Universe a few years in, where things have happened but they haven’t been involved because they are only just starting to form as the Xavier school, and have been largely in the shadows, intentionally staying off the radar. (The closet, if you will)
Also would make it a super easy way to utilize the mutant metaphor in a 2019 world as a new rising civil rights phenomenon. Blue people are suddenly turning up that look like demons in Germany. Wtf is that, some sort of Norse giant? Another Thanos thing? Why are these mutants showing up? Is it because of the snap? How long has this been going on? The people of the MCU have some reactionary, and narratively justifiable reasons to fear mutants as they’ve seen the consequences to the actions of these super beings.
It would also be an easy way to start from scratch, introduce the characters at their origins points in a new context compared to the Fox movies which were centered around a timeline established in the 90s and played with the decades.
Magneto could still reliably be a focal point, while also very easily not needing to be the main villain. I think Kitty Pryde and Nightcrawler would be the most logical character focal points imaginable. Wolverine and Storm, Cyclops and Jean, Colossus or Beast. Keep the core team pretty tight for X-Men standards, the usual suspects Guardians of the Galaxy style.
Get the Wachowski sisters to direct it for sure.
Honestly do it as a series if they can.