It wouldn’t make sense now that Rey is the adopted Skywalker, but before ROS i would have said i would have wanted to see Luke as a father. Whether he would have had a son like in the EU or a daughter i don’t really care. His wife deceased or not could have been sort of like Mara but didn’t have to be Mara.
I never liked the celibate monk prequel thing.
Would have liked to see Luke rebuild the Jedi order, search the galaxy for the lost temples and artifacts. Learn the deeper mysteries that the prequel Jedi had forgotten.