This would be the perfect payoff, IMO. Ever since House of M, X-fans have blamed Wanda for killing 90% of Marvel's mutants. (The editors were really to blame, of course.) Introducing mutants to the MCU through Wanda's "hex" bubble would be a perfect subversion of that awful story.
I have always hated the fact that Marvel's writers and editors have used Wanda's powers and supposed insanity as blunt instruments to kill off characters they had no use for. This started with Hawkeye, Scott Lang and Jack of Hearts and carried on with unwanted mutants. Feige, being the ultimate fan, could be rectifying the injustice done to Wanda in the comics, just as Iron Man's reputation was repaired in the MCU.