Honestly I think it would make more sense to introduce her as a new side/main character in the Rebels sequel. If it is a direct sequel to Rebels, following Sabine and Ahsoka’s quest to find Ezra, maybe she could come along on the journey.
Personally I would love a more general post-ROTJ series that brings in vibes of the popular post-Endor EU stories. It could be a perfect way to show the further adventures of Luke, Han and Leia, and their story could converge with that of Ezra, Sabine, Ahsoka and Thrawn.
Right, and I can see it working, I just personally think Filoni’s series are better when he’s just left to work with his own characters. So far the only “higher priority” characters have been movie related, which makes sense, and even then Rebels had very few new movie references other than Saw (which was technically a CW character first anyway). I do like your post-Endor suggestion though, and I’d love to see him do something similar to CW with Luke, Leia, etc. He’s already shown that he can do Leia, Lando, etc. really well, so seeing the OT gang alongside Rebels favourites like Ezra and Ahsoka would be a great foundation for a new Filoni cartoon. I just personally feel that adding a bunch of Marvel comics characters would just muddy it all up, better for him to prioritize his own continuity and the relevant live action stuff that most of the viewers have probably seen anyway.