As much as I really like the aspect of the game being entirely Europe, I can't see it being the case. I feel like they would try to be equally France as they are England, so will they have a London-esque city as well as a Parisian one? What about Ireland, Spain, Portugal, Italy, Greece, and these other influences? The region would consist of really large cities like Castellia, and I think a lot of players, yes appreciated a large city, but I don't know if they could handle multiple large ones. Even Goldenrod size is kind of extreme.
On a side note I saw that earlier there was discussion about gyms being in different buildings, like a cathedral or something, and I totally agree. Gen V did a fantastic job at starting that (Roxie and the Bar, Lenora and the Museum, The Trio and the Restaurant) What if the Versailles building is a ghost gym (Hence the Golurk statue) Other gyms could be other notable buildings too.