@funnypielord1That would rule out Growing up a Master, since the MC's father loans him his subs on a temporary basis so the subs can help teach him how to be a good responsible Dom. It falls under your prohibition, in that the subs are loaned out, but the reason behind it occuring is very different, it's not intended to humiliate the sub or establish dominance, and if the subs were misused, there _would_ have been swift negative repercussions. It worked out because the MC was, at heart, a nice guy, who _did_ care about his father's subs, and while learning to be a Dom, recognized that there is a two-way relationship between Dom and Sub.
I'm not active in the scene myself, my knowledge is purely academic, so there is the possibility that there _are_ subs who desire to be humilited in such a manner; they'd need to find a Dom other than myself, if I were to be a Dom.
I agree about The Favor; that didn't need to occur, that was an abuse of the relationship; she wasn't setting out looking for humiliation as part of the deal, at least not as I recollect it; it's been at least ten years since I've read it. I haven't read The Avatar.
My reading tastes have changed, so I'm no longer actively seeking out D/S stories; I was never into S/M. If an author I know and trust writes one, I'll read it. An example is Tedbiker's Petgirl; he's one of my favorite authors so I read it when it came out. It's precisely the type of story you are looking for, I think. He's written a couple of others, some of which you wouldn't be comfortable with; the societal context of the stories explains why what happens, happens, but those involved actually start to take steps to change that context so it won't happen in the future.