No need to overwork yourself -- as much as I'd enjoy some good ogre rape -- bad endings aren't totally necessary and the NTR hater crowd will still give you shit for having some one else sex the girls even if it's a "bad ending".
I think having the choices you have so far, choosing which girl you want to see in any given scene, like the first where its Yharnam bj, Morganna bj, or both. That's enough to make it a 'game' rather than a kinetic novel. If anything you could have those choices lead to different endings, e.g., solo girl, or harem routes. IDK. Just spit balling really.
Personally, I'd love to see you keep plowing ahead with the main story, rather than back track for bad endings and getting bogged down in divergent paths.