That makes a lot of sense, although it feels unearned if the major event of the Hellfire Gala is something that doesn't come from a development in an X-related series.
To be honest, the Wanda idea is just a means to an end of reversing that stupid retcon. I also can't think of any reasons for him to kill her unless he's telepathically forced to or something.
To be clear the Red Skull thing is just me spitballing as something that actually makes sense for Mags to do, rather than randomly murdering the woman he thought was his daughter for the last decade.
Skull is somebody he has a lot of very good reasons to kill, and whether Magneto has a defensible reason to do so isn't really black and white but lots of shades of Grey. Mags just chewed out Cortez in SWORD, citing his holocaust background in conjunction with current path of forgiveness for humanity.
That forgiveness likely wouldn't extend to Skull, who was directly involved in the concentration camps Magneto was imprisoned in as a child, AND defiled the grave and body of Xavier AND stuck a ton of mutants in concentration camps during AXIS. Magneto has (attempted) to outright murder Skull twice for both of these events, which is extreme even for him.
Skull should *probably* be dealt with in the Captain America books (and probably will be), but the premise behind the gala is Krakoa throwing open the gates to humankind for the first time since inception.
The list of notable *humans* (or non mutant post humans) introduced in the X-books (especially those that would be invited to Krakoa *and* show up) is still pretty short at this point.
Skull (in his current guise as an influential member of the power elite and famous media personality) fits that bill pretty well- especially since Selene Gallio was the one who resurrected him AND Selene is a member of the Power Elite alongside Skull AND Selene was the one who murdered Hydra Cap (presumably in cooperation with Skull) AND was the one who (accidentally) restored the youth of Sharon Carter AND mind controlled a town full of people in the Cap books.
Basically Selene has been all over the Captain America books as a prime mover. It's not an X-book but i always did think that was more than a little strange.