Unfortunately, I never got very far in doing any more than thinking up stuff for the last movies, but I actually put some words down for the third film, X-Men 3: Operation Zero Tolerance (Inspired by the 1997 X-men crossover story line). Focusing more on Cyclops and his reaction to Jean's death from X2 (ooh…spoilers??), it also introduced the Hellfire Club, showcased a Danger Room sequence AND had Bolivar Trask as the villain -- that means SENTINELS!!! There were a few other tidbits I tossed in there, but it still stands unfinished at 50 or so pages.
If you care to give it a read, hit the jump and check it out! HERE
There were some definite "Man, What if…?!" qualities there and I remember asking myself if I truly didn't like X3:The Last Stand because I didn't ACTUALLY like it, or because it wasn't what I had wanted to see happen? Lol! Hopefully, at some point, I can return to it -- I'd like to finish it up, just for the sake of having done it and who knows…it could actually BE something one day!