The MCU could fix Scarlet Witch's death in the easiest way, but it would cause a huge problem moving forward. In the climax of Doctor Strange in the Multiverse of Madness, after her fight with Strange and America Chavez, it seems that Wanda dies, sacrificing herself to destroy the Darkhold. Audiences have been pondering on how the Scarlet Witch can return in the future after this, what seems to be the end of her story.
Now that the multiverse door has been opened in the MCU, countless different versions of every character exist out there somewhere, as is shown in Multiverse Of Madness with a different version of Wanda still with her children from WandaVision. The entire Loki series is set around there being multiple versions of the same character, or variants. This is also the case in Avengers: Endgame when a new variant of Gamora is introduced from a timeline before she met Peter Quill and before her death in Avengers: Infinity War.
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Scarlet Witch's MCU return could be pulled off if another version of Wanda from another universe were to take Earth-616 Scarlet Witch's place, but this could start a troubling trend for the MCU. It has already been theorized that this is how Natasha Romanoff could potentially return. This would make three of their main female characters different from the originals and could send a message that they are interchangeable with their variants. This could give the impression that all variations of Marvel's female characters are one and the same and getting rid of one doesn't matter because they can just bring in another version and carry on as normal. Gamora is slightly different, as she’s the same Gamora from the 616 timeline, only before meeting the Guardians of the Galaxy and reconciling with Nebula, rather than a completely new version from a different earth. That could bring some nice drama to the film, with Gamora being Guardians of the Galaxy 3's villain potentially, but when paired with the potential return of two other characters by multiversal means, it could sour the taste. This is a problematic stance for the MCU to take, especially if they aren't doing it with any male characters but are with a handful of their female leads. Loki and Multiverse of Madness show how different each version of their title character can be, so to go back on that with Scarlet Witch would be a step backward.
How The MCU Can Fix This Scarlet Witch Problem
The best way to handle her return would be to resurrect the same Scarlet Witch from the main timeline where the character is already established. This stops the problematic implication of interchangeable female characters before it begins. The MCU would avoid the problem of by trying to keep the characters the same, actually ruining them. If the other Wanda from Multiverse of Madness returns, she may not have existed with Vision and Wanda's kids in the same way, and it would take away a lot of the character development seen in WandaVision. She may have lived a completely different life, furthering the problematic approach of all of Marvel's female heroes being interchangeable, and therefore insignificant and not unique.
One other possibility to consider is that Scarlet Witch didn't die at the end of Doctor Strange in the Multiverse of Madness, meaning the problem of the easiest death fix wouldn't need to happen. Either Marvel could explain in a future film how she escaped, or even just resurrect the character somehow; after all, she's one of the most powerful magical beings in the entire MCU, if not the most powerful. One thing is for sure, though, the best course of action moving forward would be to keep the Wanda the audience knows and continue telling the story of a great character.