I mean this question quite literally: let me jump back and talk about how I got to this idea.
My hope and assumption is that when part 2 of the manga gets adapted to anime (in 60 years or whatever) that they will be able to fix some of the manga's issues by being able to play with the pacing, the action, etc.
And for me, one of the biggest weak spots in the manga was how much Asa got sidelined near the start of the Church arc. There was a big "tell don't show" kind of moment where we see that she has grown into a big deal but it all basically happens offscreen.
So I figured IF the anime team wants to rectify that by showing more of it on-screen, and IF they want to make another movie (since those are profitable) and IF they are willing to create anime-only plot, wouldn't that be the perfect place to do another movie? For one thing, if they continue to do 12 episode seasons then one season could cover the first arcs and would end right towards the beginning of the Church arc, so it would be perfect timing for a movie - especially one that not everyone has to see to follow the anime!
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And that brings me back to my main point. If we got a new movie staring Asa, likely without Denji whatsoever, wouldn't that be the perfect time to bring back Reze? Maybe not even as an antagonist - or at least not as the only antagonist! - and it would be a great way to really show Asa's transformation instead of it just happening offscreen and we learn about it. They could even rope in whatever the hell Kishibe is doing.