Very interesting.
Curious about this Xander's origin, being the son of the Super Soldier and a mega genius. How did that happened? And what other AU is there besides Toni Stark?
Which also begs the question, how did Xander get to L.A. and become Riot? When did AU come in?
The Avengers and SHIELD seem to know of the "Slayers", and that Buffy is one of them, also needs to be explained a bit. At least the Slayer line was split if not expanded as they called her "a" and not "the."
Looking forward to more.