in the dungeon scenes:

gags.

the fuck machine would include a feature that allows the girl to be fastened to it, wrists and lower legs manacled to the floor or something similar.

the stocks would include ankle traps.

the girls could be roped tied (hogtied, tied to furniture, strappado, etc.)


in general in the fast sex scenes:


an ai for the girls that is more responsive to speech. the girls should be able to respond to questions or comments concerning any activity that can take place in the scene (based on their preset attitude). For example "do you like being spanked?" could elicit a reponse of "i love it" from an eager girl, "i don't know, I never been spanked from a doubtful girl and "no, don't you dare try it" from a frightened or angry girl".

the responses to commands/requests would also take into account the preset attitude. happy/eager girls can be told what to do and they do it. doubtful girls might need to be sweet talked or cajoled into compliance. frightened or angry girls would perhaps have to be threatened or punished in order to gain compliance. if physical punishment is used to gain compliance this might adjust the girl's attitude towards future commands.
the girls should be able to beg for an activity to stop.

the girls could be forbidden from having an orgasm without permission, and the orgasm peak would not pass until permission is given. angry/scared girls might disobey, eager/happy girls would probably not disobey and probably hold out longer before asking, doubtful girls would probably start asking at the first signs of
impending orgasm.

the girls would faint or pass out during particularly strenuous or stressful sessions.

good points

Easy missionary, maybe have the girl move like the anal pose.
Cowgirl position, make the girls get off their lazy butts for once. lol
(idk about anyone else but moving back and forth by walking isn't right to have sexual intercourse so the controls for sex need altering) that's a real bugger for me. Can't stand that we walk backwards to pull out then move forward to penetrate? Honestly it doesn't make sense-who has sex like that?