A little customization to our succubus would be nice before the contract signing (skin/hair/eye colors, hairstyle, bodystyle (thicc, thin, tall, short, muscled, milf, etc), breast size, personality inclination, etc), though I can see people wanting more focus on actual content first. (And possibly file size concerns.)
Would be nice to have more foot content than staring down at the tops. Usually soles or toes are what people are looking for in this with a position where she'd be sitting. May require some toe rigging down the line.
Futa has some additional options it could take with oral, pegging, and worshiping, though it does say it's in "beta" atm. I'm sure some will want options of balls/no balls and vag/no vag for this too depending on how much you want to cater to. Personally, her red light green light mode has her a bit too head on- a slight angle of her position to see more, or more hip swivels to tease the viewer with what she's sporting would do wonders to spice it up a little more.
Censor options could include black bar mode over blur, levels of censorship (how much gets blurred), and types of censorship for certain body parts. The main type would likely be 'sissy' mode which hides the tits/vag, but not cock, while some might be into no belly button, no hands, legs, armpits, feet, etc.
Windowed mode on PC would be nice, esp if she wants you to do something like play a game or watch something by minimizing to just her screen without the black sides and putting it off to the side. However, full screen mode does demand more of your attention on her.
Most reward endings seem to have her leaning over a chair and looking away. While not terrible, a better angle at her butt, her looking over her shoulder, or just different positions with her watching you/looking down at you could be nice.
Closer hypnosis could be a more direct/intimidating version with her cupping your chin and staring face to face with her eyes taking up most of the screen.
Heels, standing oral, leash tugs for collars, face sitting, requiring and giving pronouns (mistress, pet, etc) are all some other ideas off the top of my head.
Can't wait to see where this goes. It's very similar to Femdom Waifu, but I think this has way more room for opportunity.