- "The need for sex could be determined by lust, which slowly increases over time; it just makes no sense that having multiple orgasms makes you hornier."
I absolutely agree with this. What I believe in current Lust system this stat is a amalgamation of Horniness/Sex Drive/Sex Appetite and Sexual Energy (read Sexual Satisfaction quantified and given supernatural properties with similarities to Mana). As it is currently it is quite illogical that Sex interaction and Public Sex Humiliation increases Lust while some other sexual skills like Reward with Sex and Serve decrease it. What I propose is to divide the Lust stat into these two:
Sex Drive - Increases with time, the rate and its dependency should be roughly the same as current Lust. It also passively adds some Consent. As the servants become more horny they should be more agreeable to sex actions. If the servant experiences orgasm and has enough SD(Sex Drive) it consumes certain amount of this stat to enhance the effects, like gaining more Sexual Energy (effects below), more loyalty and so on. Current effects should be decreased for balancing purposes. There is also an option for buffing prostitution, when slave is horny (has enough Sex Drive) consume certain amount it for bonus gold instead.
Sexual Energy - If there's some, certain amount will be consumed every turn/hour for buff to productivity and some obedience and loyalty or buff to (in future because there's none so far but I hope they will be added) entertainment jobs, like waitresses, dancers, singers and so on - happy girls are more beautiful, well fucked happy girls even more so, and a prettier eye candy obviously increases sales more - in which case, same as above, consume certain amount for bonus gold. Also this opens the new resource which can power Sexual side Social skills like Seduce or Charm. For example, you can even remove max capacity on those, but make cost high like 100 SE(Sexual Energy) for seduce and 25 SE for Charm.
- "Moreover, slaves that have great sex can gain inspirations to work or fight better, or just bonuses, like experience or stat increases."
I do not recommend buffing damage and def or any combat stat with current equilibrium, it is still too op compared to production so far. I do like the suggestion about experience and stat increases. Let's say well satisfied servants would be more inclined to focus on their work and improve themselves for a good master, again with the current state of the game it should be for production jobs only.