What mutants will you put on the MCU X-Men team? I think we can all agree Xavier, Cyclops and Jean are essential; Storm and Wolverine could replace Angel, Beast and Iceman (because the O5 were super-WASPy and quite male-heavy, and Iceman’s kind of redundant with Storm on the team), and maybe add Kitty Pryde as an audience surrogate, to explain what the heck were the X-Men doing all this time.

It’s tricky, because there have been lots of different rosters that people have been attached to at various times – O5, Giant-Sized, the Australia team, Gold and Blue, etc. 

IMHO, you start with the roster as it was in X-Men #129 – Cyclops, Phoenix, Storm, Nightcrawler, Wolverine, Colossus – with Kitty Pryde as an audience surrogate. That’s a solid and flexible core that you can easily add onto – Rogue, Gambit, Longshot, etc. – without losing the character dynamics.