Now that all the main girls already have routes i am hoping they focus on adding more scenes to those already done.
As i mentioned in my comment above, the main writter for Wallis said she is open to go back and add some content plus they all (devs) already show are also willing to do that too when they did the Demetria's chastity route. So one can be hopeful.
But not only her, Vicky and Suni paths are barebones when compared to all the others that came after and as you mentioned there is also the poly route between Claudia-Demetria-Protagonist still waiting to be done.
I may be wrong but i don't really see them making the landlady Betty who was always just a bad ending into a full route. I mean how would that even work? She is a psycho who lures young and lone boys with the promise of a nice place to live just to turn them into living furnitures.
Stacy could be. We know nothing about her other than she is a small shop owner who doesn't mind accepting money investment from a male and that she likes a bit of roleplay.
ps:
Renee's route, i think, would be even darker than Wallis's because she is a unrepentant mafia boss. Torture, assassinations, drug and people traficking, corruption of public officials etcetera. Her list of crimes is big.
Personally I'm hoping they focus on a damn scene gallery.