"Always listen to the crazy scientist with a weird van or armful of blueprints and diagrams." -- Vibranium
I’ve been trying to work out where I would end it myself
I feel like ending it with Paul becoming Muadib would overall hurt the second movie as I think a big part of that movie would have to use those plot points to make up the meat of the movie. I could be misremembering the structure of the book, but from what I remember it was quite a bit into chapter 2.
I thought the most organic ending would be after the Assault on Arakeen and Leto’s death, but then the Fremen would feel fairly out of left field in the second movie. So I honestly have no idea how to make the ending of part 1 feel more organic, without bloating the run time to 3 hours. And any way I can think of has a negative effect on the second movie
In the end though it won’t matter as long as part 2 is good! I feel they’ll add up into a great 5 hour story as opposed to two separate movies