The women in the X-Men world are often far more interesting than the men, and even have better powers (maybe that’s why an all-female X-Men comic is on the way). Storm seems like the obvious choice for a solo film, though Halle Berry’s reluctance to play the role quells my interest in seeing one, and the butchered Phoenix story is sure to make fan’s uninterested in a Jean Grey/Marvel Girl film. This of course leaves one more major player from the franchise, Rogue.
Throughout the franchise, Rogue is the one that has had the least fulfilling character arc and has gotten less interesting as the series progressed. This can be fixed. Her origins, of course, were covered in the first film, but I think if the character is going to make the leap to the big screen in her own adventure, we need to see her with the added powers she’s known for. The super-strength and flight powers that she permanently absorbed from Ms. Marvel in the source material could be written into the script in any number of ways, but what is most important is that Rogue is no longer a dependent and helpless character.
When written well, Rogue is a prime example of a strong female character and Anna Paquin is no stranger to playing these types of roles (just not with all of the flying and punching). Unfortunately, a film based on Rogue would be unable to use the comic book origin wherein she’s recruited by Mystique to join the Brotherhood of Evil Mutants (unless Fox says “Screw it, do whatever you want”). But the best way to promote this movie and make it work is give her the long time relationship she’s had with Gambit and cross promote these two characters not unlike Marvel Studios.