Polaris
The X-Men universe from Fox is likely no more. Patrick Stewart has cemented his decision on his involvement with the MCU and Professor X. That allows brand new stories to be told with characters that have no doubt influenced the superhero stories we have today. We don’t know how or when we’ll start seeing these characters enter the MCU, but the odds are pretty good that Charles Xavier and his best frenemy, Erik Lehnsherr AKA Magneto, will play a role. If we assume these characters will take a cue from their Fox counterparts, they will be older characters. It wouldn’t be out of this world, then, for Magneto to have a mid-40s daughter out there.
As the daughter of Magneto, Polaris is a conflicted character. While she considers the X-Men her allies, she has been their enemy from time to time. Some of those times are due to being mind-controlled, but the resulting damage to her mind also contributes to her actions.
Polaris could be slotted into a potential X-Factor series on Disney Plus, which would suit Jennifer Aniston’s television roots well while leaving the door open for the character to appear in a future X-Men MCU movie. Aniston has also mentioned wanting to do more comedy, and one can see the character being reworked to play a part in a potential Deadpool lead X-Force movie—assuming Marvel plans on moving forward with their version of that.