Part of what you wrote is an origin story (before they became X-Men, Charles gathering them) and the biggest logistical problem we've been talking about is where did the X-Men come from?
You can't just jump right into a origin story. Even if they wrote the movie exactly how you said....and it's amazing....at the end of the movie you gotta figure out how to get them from where they are, to the MCU.
And, this is just my personal opinion....but as large and expansive as the X-Men universe is....I'll never get why people want to see the same characters and versions of the same stories that have been in the movies the last 20 years. Or if they're gonna retread the same ground at least introduce Genosha or something.
Fred.
I actually dont think the mutant origin or epidemic should be addressed in the xmen movie 1st.
It needs to be established outside of the xmen movies that mutants are a thing and around. That way coming into the xmen movies it won't feel tacked on or out of place.
Trying to explain were mutants came from, the origin of the xmen and then some is alot for one movies plate.
Especially for characters that alot of people already know some of the history behind.
Think about it like how they did spiderman in civil war.
They established that spiderman was a thing and connected to the bigger picture before they released his movie. That why they didn't have to try and make it make sense to the viewers that he's always been around, and they were able to skimp on some origin stuff too because of the characters popularity and it already being established that he's "around" so there enough familiarity.
The same should be done with mutants, they mutant threat or rising needs to be addressed even if slightly in an avengers movie or something before and outside of the xmen movie.