DevoidLight
Gym Leader
Even if the new paths aren't available until late in the game, I still think it would be cool if Berry Vista and Twirl Forest were part of the open world. The way they are accessed now almost makes them feel like DLC, separate from the main game. Berry Vista for example could be accessed by surfing from Cherrygrove City. It wouldn't be available any earlier in the story, so it wouldn't drastically affect gameplay, but it would make Berry Vista feel like a part of the Johto Region.