Dress up games are awesome! I’d love to see the dynamic between the two characters in this VN translated into a dress up game. It would be awesome to dress her up step by step, applying restraints and flirting with her about her outfit. It would also really help the choices/agency of the player to be able to choose the kinky restraints you put her in, from the type of gag to how her arms are restrained.
And as for storylines, it’s what you can expect from visual novels like dating sims and the like, but I understand it would be hard to implement. Going through and making different endings means making new illustrations, and that would practically double the workload just to make two different paths. That doesn’t seem to be the direction your passion and workflow lies in and that’s all good.