The mind control stories always involve turning the person into a Stepford wife/roboslut.
Wouldn't it be fun if instead of that you created a slave that essentially wrote dirty stories for you?
"Mom, tell me the dirtiest thing you would ever do on a dare"
Then the story centers around the mother compelled to tell that story.
"Mom, write a story about blackmail"
Then the story is another vignette of how the son blackmails the mom to obey him based on the last story she wrote and he no longer needs mind control. Etc.
You could also make her write the stories sitting on a stool naked with her legs spread very, very wide at the family computer when nobody is home.