I'd say make it as one of the routes players (MC) can choose.
The game is about swinging so most peple here already came for the cuckold fetish in the first place, making it easy to transition from:
Only doing it because husand likes it ->
As long as he knows about it ->
Feels good so why not ->
Chasing pleasure and leave him for good
also +corruption tag so more people might find out about the game
People only hate NTR if it shows up in the game unexpectedly without any warning (can add warning next to choice) or they downloaded thinking it's vanilla (already taken of thanks to the title lol). If you let the corruption happen naturallly and 100% up to player's choice then no one will complain, hell they might even love it even more because corruption + NTR is like bread and butter.
View attachment 4555879
If you're still not sure then you can always poll it. Personally, I want as many scenarios as possible because this is AI CG game so many will looking forward to the story and lots of CGs.