Perhaps Disney could hire J. Michael Straczynski to help them craft contingency plans into the MCU. He pioneered the technique of building "trap doors" into his scripts to deal with this very problem, when creating the multi-season story arc on Babylon 5.

You missed the key movie that Chris Columbus made: Young Sherlock Holmes. Certainly a movie set in a British boarding school with three young people seeking to thwart a mysterious villain

I have a theory that it is Agatha who ends up bringing Wanda back, to steal her powers. However, Wanda refuses to attack her, leaving Wanda very much alive and kicking. Rio, in particular is thrilled and manages to take Agatha as her plaything.

This would leave Wanda's family restored (sans Vision) and Agatha sidelined for the moment.

VERY interesting theory. I've suspected that Teen was Billy and had plans to get his mother back; I'd thought perhaps that he IS seeking power, but left off the bit "... to bring back my mother".

I do, however, suggest the possibility that he does bring Wanda back as the Scarlet Witch, but brings her from another dimension, as occurred in Spiderman: No Way Home. This Wanda would be guilt free and able more easily to re the Avengers and get her picture back on the lunchbox.