Ok so I think everyone is looking at this all wrong.
Wanda is an avenger, and while there is enough content in her story to justify a full fledge movie, there simply isn't enough room for her fo have one. So with the creation of Disney +, Wanda along with OG characters and new ones can have their individual stories told while maintaining their forward connection to the MCU.
This is basically a wanda past, present and future arc. A way fo expand the character further while strengthening her role in the MCU as a supporting character.
The tie in to Doctor Strange could very well have little to do with this show. Strange could simply seek out her help based on the threat level in his movie.
The last Episode could very well end with her finally having closure, and going down a path of harnessing her abilities. With possibly Strange being a mentor to her.
Agatha could be defeated or possibly become the female Loki, or even killed off for all we know.
And it's just that simple. People expect this TV show to
1. Introduce the fantastic 4, even though there isnt even a release date or even a script for the movie.
2. Mutants, even though no xmen movies have been mentioned at all.
It's too early for that. Maybe mutants will be revealed in The Eternals. Which was supposed to come out around the same time as Wandavision.
And it's funny becasue when the Disney/Fox deal was announced, a lot of people didnt want these characters in the MCU. Now all of a sudden, everybody wants them shoehorned into everything
Just becasue the DC movies will have random characters show up out of the blue, doesn't mean Marvel will start doing it