Another suggestion:
A morality system.
Player characters start in the center and different actions and events can nudge it towards good or evil, Unnamed NPC's start at a fixed point can cannot shift in ether direction, Named NPC's start at a fixed point and can shift further towards evil or good depending on player actions.
Examples:
Cassie
Starts out with a +20 good alignment and if the player:
Uses her sexually it falls towards evil and she may become lustful.
Is kind to her and gives her nice gifts she will become more good and act more trusting and adorable around the player.
Rinny
Starts out with a -20 evil alignment and if the player:
Uses her sexually it falls towards evil and she may become lustful.
Is kind to her and gives her nice gifts she will become more good and act less mischievous and more adorable around the player.
Uses a scale between -100 (evil) to +100 Good with 0 considered neutral.
Example:
After defeating an enemy NPC choosing to do something sexual to them increases evil morality, choosing not to increases good morality.
Becoming more evil increases lust/ero damage dealt, decreases lust/ero damage received & makes skill checks vs evil characters easier to pass.
Becoming more good increases physical/stamina damage dealt, decreases physical/stamina damage received & makes skill checks vs good characters easier to pass.
Bonus effects peak at 10% with the exception of being full evil which gives a passive mana/spell energy regen (1 point per turn/moved square) and full good which gives a passive stamina regen (1 point per turn/moved square) - bonuses are applied while at 100% good or evil and lost if less then 100%.
Edit: A few more suggestions and as I don't think it's worth a new comment ...
'Bald' head hair style - The character does not have hair on the head.
Nipples for flat chest - They are missing for that setting.
Watersports - Described only unless to what to draw / animate it and behind a toggle for anyone who does not want to see it:
Had to much to drink ? Use a toilet (maybe a bursting status effect ?)
Act of humiliation (Forced to relieve themselves in public) / submission (showing 'weakness' to another) by the player character and/or NPC/s