What if instead of those random Pokecenters that spawn in the middle of no-where, you have base camps set up all over the world that are inhabited by researchers, trainers like you, ect.
At these camps sprinkled throughout your world, you can heal your team just like at a regular 'Center you'd find in a town, but these places could also have NPCs that would sell you wild forgeables and the like? Stuff like berries or tumblestones they've collected.
Just another small way to make the world feel inhabited by other trainers.