Why make wife cuck? This is just the genre of the game! The intention of MC is to break down his wife's sexual conservatism, and the cucking is a consequence. That's the kink! Marriage (usually) means sexual exclusivity, by the way.
That's fair, of course, and if that's the only way you want to take this it's quite understandable. But you're making a really nice platform here that you could explore other options which might also expand your audience.
For example, cucking the wife would be a really interesting take that fits the scenario perfectly and is very under-represented in porn. While that's not my thing per-se (although better than MC being cucked which is entirely unenjoyable to me) there is some really interesting middle ground. Influencing her into dom/sub, influencing her into additional female partners but not male, or just going "everyone happy" swinging/polyamoury. Of course, these would require a little bit of tweaking to the existing scenes. For example, even though I played this without her cheating even a little, I pretty much lost all sexual excitement in the game when she started intimating that the MC was unable to satisfy her sexually. But other than a few of the existing scenes, this really is a wonderfully adaptable platform that puts me in mind of the potential of Wife Trainer.
If you don't want to water down your efforts or these other routes just don't interest you at all, that's fair enough. I just thought I'd express my own wishes that might be interesting to you as well.