I see from a brief stalk of your profile I've read some of your earlier work. Now following. :)

To answer a little more regarding Dune, there is a line where one of the Fremen uses the Fremen term for Reverend Mother of the Bene Gesserit, explaining they are not allowed to fight the Bene Gesserit, which is why Jamis is forbidden to fight Jessica in person (a similar line is in the novel). I also think Jessica was a lot more confident in Paul's ability as a fighter rather than how he would bear up under the severity of the Bene Gesserit box test. What would happen if he'd refused to fight? I'm honestly not sure. I'll have to reread the novel, but I expect there would have been rather a stalemate that benefited neither side.