A Maria book... There are three ways I might be able to do that.
1. Maria, Countess Ward, must reach past the shallow and "overly friendly" person that she once was to protect her people. Action and adventure replace her average day to day schedule. At least for a bit. This would be no more than a soft "R" rated book, but part of the normal flow of things.
2. Maria is herself, and living her life, while trying to recapture the good graces of the King and Kingdom, and there are a lot of scenes where she just got done entertaining, or is just about too, as the door swings shut.
This could also be doable. PG13 to R.
3. An erotic novel that has too much story to be considered porn, but way to much graphic sex to be even "R" (for a book, I mean.) This would be a bit like one of the later Anita Blake novels, or perhaps a bit stronger. I could put it in erotica, place warnings all over it and so on.
That should be enough, as long as the people that don't like that kind of thing don't hire hit squads to ruin all my ratings over it.
I have to say, I'm sort of tempted to do that last one. If so, I think I'll keep it shorter than most of the other books. (Around 100,000 words or so? Maybe not.)