I could see that. Vecna didn't bank on her body surviving since he just needed her for the ritual, but considering Max escaped his grasp once and very nearly did it again, it wouldn't surprise me if they had him use her body as a puppet to taunt and fight Eleven and her friends. I mean the Mind Flayer used her brother in Season 3. Would be almost poetic to have Max used in that role and it could give an opportunity for Sadie Sink to do more without the real Max being present/safe. As I'm thinking about it it seems almost too perfect for the Duffers given the critical reaction to Sadie's performance this season.Have a feeling 11 resurrecting Max...isn't going to go as well/obvious as people think...
They never actually showed her come back, I wouldn't be surprised if she is somehow a villain in the final season....who knows what exactly 11 did to her..
Though I'm left wondering what they'll do with Will's remaining connection to Vecna and the Flayer. The whole Harry can sense Voldemort thing was good for a while but it feels like they need to do something more compelling with it for the finale.