Cuz Storm is awesome...she's one of the highest profile characters that got the crappiest treatment in the movies. Storm has been a top fighter, leader, morale officer and powerhouse for quite a while... the movies captured very little of that.
X1: She had an accent, as Storm should have. She's was actuallly wise to a point, and challenged Wolverine on a moral/thinking level. As Storm typically challenges everyone.
X2: She's had a character arc, small as it was, as Storm should have. She also had a part abou the right size for an ensemble movie (which the X-Men series failed to be)
X3: She actually looked good, with believable white hair, as Storm should have. She used her powers decently, and the spinning was a nice touch. And she was a leader... she actually acted like one on two seperate occassions. They actually tried to show off her fighting skills... meh.
In short, if they combine the best parts of Storm from all three movies, they'll have something that not only is compelling, but will actually resemble the comic book character. Unfortuntely, niether Fox nor Halle-bashers will stand for it.
I think that a continuous movie would be best, unless the franchise is going to rest for 10 years. There are successful X-Men books that don't feature Xavier, Scott and Jean (see everything buy Astonishing nowadays)... there can be movies that do the same (and Scott could be alive too).
Worst come to worse, brink in Havok and Polaris to be your new Scott and Jean, if you just can't handle X-Men without those archetypes.