This whole story is a lot of work. Tons of core story, tons of side story, tons of bonus content. Again, it wouldn't stop Runey, if he thought it enhanced the game.
Yes, but by the time we've reached they also want other things. Sometimes contradictory things. NPCs have shut him out, stopped dating him, stopped being available for the dungeon, and every point in-between. BDSM as a binary switch — yes/no — is very unusual for this story. "I love being kinky but I'll no longer humiliate myself" would be a very realistic thing for one of the more narratively tormented NPCs to say. And whether or not that sticks — whether or not the NPC decides she actually did like the more humiliating kinks — would also be narratively interesting.
Why, though? I mean, it's easily justifiable and entirely reasonable. But why has Maria's trust never really wavered, save for a few days of isolation? Android's? Given what she's seen since, the MC put Lin in a very dangerous situation with that slave competition.
Complexity is welcome, and this story is very complex when it comes to characterization. Maria might never want to be bound again, considering what happened to her. Android might never want to have control taken away from her (or she might specifically want it, given that she's strong enough to break out of it). Lin might reject anything that makes her subservient, or she might actively seek subservience knowing that she's become the MC's equal in real life. These are all ways to make events and characters more complex and more nuanced. "Yes/no" w/r/t BDSM in its entirety isn't that complex.
Yes, it'd be a pain to retro-code. But Runey's done that as well. And the future offers a lot of potential.
Sure, and I do as well, but it'd be so very powerful.