This is something that I've often thought about. How do two people who tried to make it work and decided it didn't, how do they react to being put into proximity together?
The setup: they married young, right out of high school, no children or cheating. Two or three years was enough to make them think they were too busy. Or was it personalities? Compatability? Those questions will always linger. Add to that they both get jobs which put them into close physical space on a daily basis that forces them to deal with each other.
I'm envisioning a military-type game where both are on a Navy ship. Perhaps a cruise ship based game if that doesn't appeal to you. The exact details are negotiable but you get the gist of what I want. I think this will have loads of UST and BST, not to mention all those other activities Elliquiy is known for