It's LW, so you'll probably get jeers and downvotes from pro-RAAC crowd. But you'll get upvotes from both BTBers AND i-like-cucking-for-erotic-reasons (not always same as i-like-cucking-because-i-hate-men crowd); so you may come out ahead in the ratings, especially if it is well written. Importantly, justify "the husband sitting there and not reacting" decision well in the story - e.g. explain that he had no other option, and this was just a necessary evil to tolerate so as to not fuck up his revenge; or maybe they already had sex and an extra one wasn't making any difference. The one that seems effective (but I personally dislike) is where the husband for some WEIRD reason "still loooooves" the wife and watching in person "helps him get rid of that love". Not my cuppa tea but people seem to lap that plot approach up.I'm thinking of writing a story for LW, based on an idea someone posted here:
Parents are taking their son to college and the way the car is packed, mom has to sit in back on son's lap. You might be familiar with this story.
The twist is that the husband knows and hears everything they do in the back while he's driving.
When the parents return home, all her stuff is in storage and he gives her the divorce papers. Meanwhile the son opens an envelope from the dad stating that he is an adult now and can pay for college himself.
Incest, backseat sex with mom, cheating, and BTB. Maybe it'll do well, maybe not.
Personally, I'd love to read a story with that idea, so I hope you decide to proceed to write it.