I personally see no real reason to include this. While it might be nice to add from a historical point of view, from a gameplay point of view it makes no sense. Two different countries being able to upgrade RGOs, add factories, etc. would seriously complicate things. Almost all examples of condominiums can be easily simulated by features already in the game.
Bosnia would be controlled by Austria, wether or not Hungary was a dominion.
Egypt would be a sattelite of the UK while the Sudan would be directly controlled by the UK.
Croatia would be a German sattelite (not Vicky time but still can be simulated by this game).
Oregon Country would have both American and British claims on it, using the new claim system.
Sakhalin Island had an unclear border but control of the North was Russian and of Japan in the South. Province border down the middle.
Togoland was unofficially split down the middle after two years of occupation. 6 years later officially.
All other examples of this legal framework were mostly small Pacific islands, inhabited by about 50 people.