I agree that ideal formula for a NTR game is to allow the player the CHOICE to whether or not throw the girl into it.
I don't need to be cucked the first play through. I am the player. I can decide whether or not I want her to be fucked up.
Games just need to respond to the player. The medium of using VN works if they do branching storylines. Sadly most developres do these "routes" system where story telling becomes predictable.
Imo, the best writer in this entire system is Eva Kiss from GGGB. Yes, NTR is not a focus there, corruption is. But Eva Kiss is so talented that she can weave these stories almost seamlessly into the experience. The characters WILL reference you on things you've done, like fucking someone you weren't suppose to fuck.
A good Japanese developer that I like with choices is
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The developer uses a very fun "detective" system where you go around the house to find things out of place to unlock a scene. For example, your wife has some white liquid on her face in one of the scenes. If you click it, you see that she was swallowing cum 30 minutes ago before you came home. Probably the most unique system so far, is that detective system.