I know integrating the X-Men could be tough, but I've thought of a few ways it could work: 1) They've been there in hiding all along, determined not to cause a fuss. The latest reveal of Thanos as a world-defeating annihilator pushes them into action. Maybe Cyclops leads the young team out even against Professor X's wishes which helps fuel Scott's story (which I think has been lacking for decades). 2) Ant-Man/Wasp is supposed to explore the multi-verse. Maybe the X-Men exist instead of the Avengers in some alternate dimension. Could they be pulled across in order to help defeat Thanos? 3) The presence of super-powered people has released the genome in a younger generation (as well as a few others over time). After Avengers 4, these kids start to come forward lead by Xavier in an attempt to help rebuild the world.
I think Kingsama hit on the easiest way to do it. The Infinity Gauntlet makes weird s*** happen. Also, we have two characters in Quicksilver and Scarlet Witch in this universe already with no explanation of their origins. Can they retcon their parents' death and that Magneto didn't actually die? Maybe they could approach it like Agents of Shield approached the Inhumans where the Infinity Gauntlet does something and unlocks a dormant mutant gene causing their powers to manifest in the way the mist made the Inhumans turn. Or they could play some sort of "The Government has known about people like this for years" type angle and they are being kept in either captivity or they aren't revealing themselves like you proposed in your first option. I hope they don't go with your second option. The whole multi-verse idea can work on a TV show like the Flash, but in a sort of time constrained format like film, that's a pretty heavy subject matter to throw at the average movie-goer.
As for the MCU, this acquisition is great because of the characters Marvel finally has in their hands. Do them justice and don't get cute with it. On a broader scale this monopolization of entertainment is a little scary. But considering the whole net neutrality mess, maybe the "Disney package" isn't such a bad thing.
I do not think that the present X-Men universe will ever be dropped into the present MCU. Too much baggage and none sense. I will be a complete reboot, there might be an outside chance that an actor returns in one way or another, but that will be it. I imagine that just like @Savory Griddles says you have a reality were odd folks have popped up already, and now more and more of them are starting to be discovered. You start with a Professor X/Magneto and build from there. They could both be older at the time, say late forties or early 50's. You could also drop wolverine in too. This gives you time to explore whats going on now AND a new story to have phase 5 build on. By phase 5 you can have the "X-Men" become a thing and tell those stories.
I think you could drop Deadpool into this current MCU. His first movie was at least somewhat self contained. They even used a different Colossus than in the X-Men universe. But everything else must go.
Well thats absolutely true. DeadPool and possibly cable being the 4th wall breaking time and dimension traveling duo could easily stay the same lol. Thats actually a great idea and would allow for all sorts of great jokes and circumstances.
I'm not certain yet that New Mutants has to be expelled either. There's just nor enough known about the movie yet. I don't know how connected it is to the other movies. But definitely Deadpool can be moved over. He's very self contained but even if he wasn't, he's so irreverent that I think he fits in any universe well enough.
Hey @Barnstable I finally started watching Legion. What a weird and creepy show, I'm 5 episodes in and enjoying it so far.
She was absolutely fantastic, the big stand out for me. Spoiler It took awhile, 3-4 episodes for me to get into it. The weirdness and world building need awhile to get used to but the last 3 episodes were great. A lot of scenes were incredible and creative (really great use of music) but some were just straight out creepy. The love connection between David and Syd felt a little forced at first which was kind of strange for me, ended up working itself out. Wonder if its going to be connected with the rest of the XMen universe(s).
Watched season 1 of The Runaways. Pretty good. Thought it was going to be a teenage cringe fest but the characters are really well written. All 20 of them.