I understand not wanting to continue and how hard translating God Emperor to the screen would be but I wish he would give it a go.

As @chaogomu said, Dune Messiah completes Paul;s story arc but the comparison between Paul's unwillingness to take the golden path and Leto's acceptance of it could be a great thing to see.

Paul cling to his humanity and billions died in his name, Leto sacrificed it and changed the destiny of the humans race.