Violet will never be a main character, or official at all.honestly i think violet should just be a real character since Jin shares a room with her, however it might have a little trouble dealing with NTR
I know nothing about her, her story wouldn't be good (Not to mention the patron would likely not want me to butcher his vision of her). It wouldn't have a good ending or middle, and she isn't my character. I made her myself, but the process was dictated by a patron. Other than all of that, succubi don't exist in HH, there are no supernatural things going on, just a bit of exaggerated science.
The idea of a patron's own character is a fun one, and I think it's very enjoyable, may even do it again at some point, but they'll never be main characters due to me not making them. It's almost like some Sonic OC character being added to Breaking Bad in my eyes.
Violet will also most likely never have any additions either, the patron has stopped his pledge.