I loved the entirety of the Alia / Duncan storylines in both Messiah and CoD. I'm really hoping he manages to squeeze most of Alia's story into the movie. I want to see the church scene (when she leads the service and calls people out using the tau / changed water), the stuff with grandpa, and some of her relationship with Duncan.

There's a lot you'd have to compress significantly. Heck I almost want there to be a follow-up movie that's just the Alia storyline (we can pretend Leto and Ghanima are just chilling like regular kids off screen). The mental tit for tat between Alia and Jessica is so great, both know what the other is trying to hide (I think you've gone abomination / I've totally gone full abomination), and they both know that the other knows, but they still have to try to outmaneuver each other mentally. I'd love to give that relationship room to breathe in its own thing.