I think one thing that might help is starting the story before the kidnapping, a prologue where you establish both of the characters. This would help with some of the clunky dialogue in the beginning. Depending on how ambitious you are this would be a good opportunity to establish some degree of character customization. For instance the player could determine the main character's sexuality(straight/gay/bi) and gender identity(male/transfemale/trap) which could in turn determine how the main character reacts to certain situations. I can go deeper into this if you wish.
As for content, it depends on how extreme you want to go. Ballbusting/castration is a big fetish of mine. Could be a fail state if you piss off your captor enough. Maybe a mode where you play as the captor? But maybe that's a separate game.