I'm considering playing as Spider-Man, though I'm not entirely sure what his role would be.
Alternatively, depending on the time-line, I may take advantage of the fact that this is an AU and play as Thomas "Tommy" Maximoff, AKA Speed. There can be a number of explanations for his accelerated aging from his magical origin, his super speed, or being some sort of Time Traveller.
Hmm... maybe I could make him an Amalgamation of Tommy Shepherd from Young Avengers, Tommy Maximoff from The Last Avengers Story, and Bart Allen (yes, I know that last one's DC). He's a mutant with super speed, but his hyper-accelerated metabolism made him age too fast. With Doctor Strange's help, Scarlet Witch created a magical environment for him in which he could develop at a normal pace. There, Tommy was able to learn enough magic to stabilize his own aging. He continued studying magic after leaving the magical environment and later joins The New Avengers as their sorcerer. His primary and most-used spells are ones that enhance and supplements his mutant super speed (i.e., glyphs that propel and/or accelerate anyone who steps on them).
Or... maybe I can play as Nate Grey, AKA Cable. :p