If they ever do a Russia region.
They should have the equivalent of the Trans-Siberian rail as an integral part of how the player traverses the region from one point to another. With sections unlocking through the progression of the game. Much like Alola, but in a mostly land setting. The train ride also serve as places where the player can battle and do other things, much like SS Aqua and such. Some sections can be (or eventually be) traversed on foot to another.
It’s a large region divided into sectors.