The more I think about it, the more I love the idea of the Wicked Witch of the West as the Wizard of Oz character.
The Wizard of Oz has 5 of the most iconic characters in modern western culture. Any of them could be a great MultiVersus character. But 4 of them are heroes. Putting in Dorothy would, I think, make the game feel like it's missing Scarecrow, Tin Man, and Cowardly Lion. Including the one iconic villain would feel more "complete" than 1 of 4 iconic heroes. Obviously the ideal solution would be to include all 5, but MultiVersus just has too much to draw from to justify giving 5 characters to anything other than DC comics and Looney Tunes IMO.
I also am really interested in the Wicked Witch on a mechanical level. For her team-focused move, I think it would be really cool if she could assign a flying monkey to her teammate. The monkey could both assist in recovery and have attacks to extend combos.