"Not a single good idea" ??? Here's one

Anna is a manager, right? Jane also ...
One day they meet by chance at a local managers conference or ... party or.. both. In the ladies room, while washing hands

And they have a reciprocal "crush at first sight" (which is no wonder by the way they both look). Followed by several private meetings where they "play a little" together. They have no idea that each of them has a relation with the MC..
One day , Anna decides to surprise Jane with a visit (and a bottle of vine). MC is by Jane, they just had sex..Jane opens the door and .. "introduces" them to each other .. And here all masks fall. From this moment on it is your choice if you want to make it dramatic or .. pragmatic, but in the end a 3some Jane-Anna+MC can and should be possible