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.
I wouldn’t mind Russia, but that sounds a little too restrictive for my tastes, the problem with a lot of the recent pokemon games is that the restrictive progression is starting to feel too claustrophobic
IIRC, I used to play Pokemon Emerald (the Hoenn/Kyushu game). As I spent much of my time on the PC and PSP back then, I rarely played Pokemon, so it was perhaps the only Pokemon game I ever played. Perhaps it used to be Torchic.