I actually thought I had done one of these years ago, but if I did I haven't been able to find it. These may be old themes, but old can always be new with the right inspiration.
1. The Swap. Pretty basic but could lead to untold drama, two married couples perhaps one newly so or both long married, are invited to one of those delightful little parties where you don't spend the night with the one that brought you. There are rules of course, no seeing the other except at the parties and so on, but of course who'd find out?
2. The Wolf and The Dragon. This is one that I was going to do in another location that didn't work out, but basically it was a plot involving Robb Stark and Daenerys (GoT) Dani ends up in Winterfell, Robb wouldn't have been killed, and so on and so forth. Could maybe be expanded into a group, but I think could be done as a one on one.
The above are the only two thoughts at the moment, but I am always open to ideas, so please PM me if interested, interested in a variation of the above or if you think I might fit something you would like to do as well.