If a Pokemon region was like this it would have so much more replayability! The gym leaders would use a different version of their team based on your number of gym badges, so you could tackle the gyms in whatever order you want. Every player would have a really unique team because they'd encounter different Pokemon with different levels based on which routes they take through the region, and how many gym badges they have when they take them. Different paths would be rich with different EVs, so that would give smarter players something more to think about and plan. Also, there should be a wider selection of starter Pokemon. (I'm thinking players could start with an Eevee in this region, and each evolution of Eevee could have it's own mega evolution)