So after doing an entire entry on NYX on the fan casting angle, it got me thinking, what other mutants could 20th Century Fox use in the X-Franchise that manipulate time?
So starting off with the obvious, there's Kiden Nixon from NYX. Her powers more correlate to stopping time though. Similar to Evie from Out of this World really, but Marvel had fun playing with how it worked. She's a character that'd be problematic to bring into the franchise though as we've discussed prior with the baggage to leaving NYX intact, but also the problems to altering it. She may be a character that's best left lost in the cracks for now barring how a director could salvage it.
There's Trevor Fitzroy from Lucas Bishop's comic stories. His power works as actual time travel, allowing him to go to different eras outright. With Bishop appearing in the upcoming Days of Future Past, it seems likely that Fitzroy would be a character to follow soon after.
There's Gateway. A character still much shrouded in mystery even in the comics, but has yet to display any limits to his abilities for traveling through time and space.
There's Magik aka Illyana Rasputin, the sister of Colossus. Her abilities range over a wide spectrum usually relating or appearing as, well, magic. She's been shown in the comics several times to have done her own various time hopping stints.
There's also Suzanne Chan aka Sway(currently deceased in the comics) and Heather Tucker aka Tempo(current whereabouts unknown in the comics after the Age of X mini event) who both have the ability to manipulate time passage around objects or people. Not so much the ability to time travel but enough to manipulate trajectories and halt momentum on a smaller scale in comparison to say Kiden Nixon who essentially freezes all time.
There's Franklin Richards, the son of Susan Richards and Reed Richards. He has full realty warping powers among of which is the ability to time travel itself. For a brief time as part of the Fantastic Four comic line, his future self was in the past running a team called Fantastic Force. With Fox's recently announced plans of intermingling the Fantastic Four and X-Men franchises, he presents a strong possibility of showing up as either a child or his more adult self from the same future as Rachel Summers was from. We may even see one similar to his more recent future incarnation as shown in Future Foundation.
Last but not least, there's Legion aka David Charles Haller. As the son of Charles Xavier, he has a wide range of abilities and was also the cause of the original Age of Apocalypse comic stories.
There's also Forge, who while not having an innate time travel ability himself, he does have an ability to create any device imaginable. In the comics this has often included a time machine.
It's unknown if any of these characters may appear in the future of the X-Men film franchise, but it is indeed possible as they further dive into some of the time travel stories between the next two films and as the franchise continues to build. There are many options among the writers and directors depending on the story they would like to tell.