This is based off of a theory that one day Marvel Studios will attain full production rights for the X-Men.
How Marvel could properly introduce the X-Men with little to no confusion.
Let's say Marvel was just awarded the full production rights to the X-Men characters. This would be huge for two reasons: 1. Marvel Studios would be that much closer to having all of their characters under one studio name, and 2. We, as fans, would that much closer to possibly seeing the Civil War put into film.
But how should Marvel go about putting the X-Men on film? I personally believe it isn't through a movie. Why? The X-Men have a ton of characters, it would be hard and as we have already seen, it would leave a lot out of the public eye. I personally believe that the best way to bring the X-Men to the MCU is through television. Be it through Netflix or regular programming, like [Agents of S.H.I.E.L.D.](series:722469), Daredevil, Luke Cage, Iron Fist, and Jessica Jones. This would allow a greater time frame for Marvel to write real origin stories and later introduce them to the Avengers.
Season 1 should open up with an origin episode. Just one, with a small background story for the first mutants we would see. Throughout the season we see them struggle with trying to stay secret with their abilities. Then, somewhere in the middle of the season, someone screws up. They blow up a building or something that brings that mutant population to the full attention of the public. Magneto has his "I informed you thusly, Charles!" moment and the Brotherhood forms. The Brotherhood starts to do their thing and Charles struggles to decide whether his mutants will fight or not. Finally, Charles is visited by none other than Steve Rogers himself. This moment would solidify the X-Men's existence in the MCU, it would also be the moment in the season when Charles decides that his X-Men will fight for the safety of the human and mutant races against the Brotherhood.
The season finale would showcase a big fight between the X-Men and the Brotherhood at Charles school. Why here? Because having a huge superhero fight in New York City would be a little cliche and because you could introduce some more future X-Men this way. The two I had in mind are Gambit and Rogue, who recently came to the school seeking refuge from the mutant hate. They decide to fight with Charles' X-Men and from there it is all history. Also in the finale we would see, the newly appointed, Director Coulson come to the school and he would tell Charles that SHIELD has been and will always be watching. Maybe a visit from Stark or another Avenger saying that if they ever wanted, there was always a place for them among their ranks.
Sorry about the lack of serious detail, but I hope you enjoyed reading. If you have anything else just tell me!