quoting Izambri, Marquis, the Findible League:

A Diplomacy game using someone's conworld map would be nice. It would be an interesting way to introduce a certain historical and political context. Plus the development of the game could be used to expand the events of that period in case there have not been created yet.

I've oft considered, once I finish the map of Daia at large, making a Diplomacy version. But I'd have no idea how to make it balanced.