The book, Messiah was not as popular as Dune. Why should Villeneuve think a movie which follows Messiah would do better than Dune Part 2? I wouldn't follow the book. Dune 3 should start where Dune 2 ended not 12 years later. I would have Paul realize that he doesn't want to be Emperor. He just wants Chani who he knows is pregnant with his child. Arrakis is attacked by people from another planet forcing him to flee to Caladan with Chani, his mother, and Gurney. He also learns that Arrakis at one time was a fertile planet, but the Harkonnens made it into a desert by controlling the weather in order to make mining Spice easier. Paul plots to return to Arrakis and return it to the Fremen and change the climate to its previous condition. Dune 3 would be a happy movie with Paul as a hero and Chani as his wife. In contrast, in the book Messiah, Paul becomes a villain. Herbert wanted to show what happens when people follow someone fanatically, but there is already a historical example, Hitler. What is the point of making a dark, sad movie? Timothee Chalamet and Zendaya are very popular. People would love to see them happy together.