I feel your pain. I have a blight-based katana the scales to the user's corruption ready to be found in a kitsune dungeon that Takahiro brings you to on one of his quests for artifacts of Keros (not saying the katana is one of those, just there). Also a light-based gown set for Vivianne (but only 'pure' Viv, if she can be called that) based on blinding and light-blasts called the Will-o-the-Witch set.
Just need to finally get permission for any of the NPCs I ask to write scenes for. Apparently I like the obscure ones or ones the author wants to keep to themselves so far. Maybe if your idea is nice enough, a dev would put it in, so you could mention it in
What content would you like added?. But if you're hoping to write or get it in yourself, need that NPC sex scene.