Re: We Need an X-Factor film
Keep in mind that this wouldn't be too crowded as Angel will die early on, Gambit won't join until the third act and Forge will mostly be mission control. So the team for the most part is just Cyclops, Rictor, Phoenix, Multiple Man and Siryn.
IMO, a new timeline works as it allows the X-Men to split into three teams so characters won't be underdeveloped this time around like Colossus and Cyclops were in the original trilogy. That and now the the love triangle between Cyclops, Wolverine and Phoenix has already been done, putting them on the same team again is redundant and only Wolverine will get characterization. Cyclops and Phoenix get to grow more when they're away from Wolverine just like how Cyclops will be seen as a competent leader when he doesn't have Wolverine constantly challenging him.
For instance, over in X-Factor, Cyclops will take charge of HIS group of mutants while in Uncanny X-Men, Wolverine will find himself at odds with X-Factor so they'll still clash but this way, they'll both have time to shine.
Not only that but Sinister as Cyclops' rival that would progress onto future films, Gambit being dead and then cloned by Sinister and Angel being resurrected and brainwashed by Apocalypse would leave enough plot threads to keep X-Factor essential. Not to mention how Mutant Massacre and Inferno were crossovers between X-Men and X-Factor so they were STILL X-Factor storylines.
This isn't even getting into a potential sequel that would use Endgame, The Twelve and X-Cutioners song as source material where it's one giant crossover between the Fantastic Four, Uncanny X-Men, X-Factor and X-Force where young Cable gets infected with the Legacy Virus and his older self tells him that it'll be okay and reveals that he's the son of Cyclops. Like if Selene (who's revealed to have served Apocalypse for thousands of years) is threatening X-Force, Sinister (who's trying to find a solution to kill Apocalypse but through horrible methods) fights X-Factor, The Fantastic Four fight Kang the Conqueror (who has fled from Apocalypse's future to conquer Earth, even if that means killing his ancestor and kidnapping his son) and the Uncanny X-Men are threatened by Cameron Hodge (who's mutant death camps in Genosha are what cause Apocalypse to declare war on humanity) you'll have four films that lead into one big event where Apocalypse fights pretty much everyone.