I had two ideas, and I don't know if they've already been considered or not but I'll share them anyways.
1. Some kind of ghost transformation: I had this idea because of my first encounter with the Ivory Wraith. I think it'd be kind of cool, to have some kind of spirit transformation that gives the character the ability to do things like possession (for mischief, persuasion, seduction, etc.), but a great aversion to the likes of the church that causes pain to be near.
2. A sanity/yandere stat: This was inspired by Kylar's halloween event where you can pretend to have gone crazy from drinking the love potion. Some kind of new stat or mode or playstyle that can let you be much more unhinged. Maybe it could be related to trauma. The player could become less susceptible to things like pain and fatigue, but more to things like drugs and hallucinogens, and maybe the more unhinged they are, the more "aggressive" they are towards love interests in a way that could even disturb or cause concern in those interests.