My two cents.
Hermione. As stated in a previous post, she needs to be eased into the world of submission a little more gradually, possibly making it an even more humiliating journey for her. She should have the occasional fits of rebellion until she's in too far. Maybe the only thing that does make her stop and think is when she becomes aware of others also being trained. Maybe specifically Ginny?
Luna. Breaking her in the way she she currently is (1.42) is fine, but after that, how to keep her compliant? If she ever gets into a conversation with anyone else about wrackspurts, the game could be up. Maybe slowly leak the "truth" that sex with others won't have the same effect as sex with "Dumbledore".
Ginny. Definitely needs to be added, maybe as a threat against Hermione. Otherwise I see her as more defiant, and needs to be broken down over a period of time, maybe even with veiled threats against Hermione, Harry and/or Ron? Maybe she needs to be caught doing something she shouldn't?
Cho. I am okay with her current path, but having her as another dominant power over Hermione might be fun. Once Cho achieves her aim of Quidditch champion, she might celebrate by forcing herself on Hermione with you.
Tonks. Definitely should become a more active participant, maybe even used in the training of the girls, first as a wise council, pretending she is unaware of what is going on but convincing the girls to keep at it, then later brought in for more hands on stuff when the girls are more malleable. She should really get into sex sessions with you once certain criteria are met, such as sending Hermione to her for "further education" etc.
Astoria. I think the best way to use Astoria going forward would be as a growing threat. Once she masters the Imperio curse, she starts to become the bad guy, cursing Susan (and maybe others?) until you and Tonks and maybe Hermione have to subdue her. Or maybe Snape can step up and control her, in exchange for use of her as his own puppet.
Snape. I think the threat of him getting involved would be good, but also occasionally letting him get some would be fun. Maybe becoming Astoria's master by the end.