There are lots of ideas floating around my head right now regarding this, but I feel it'd be rather cool if they were to base a region off India at some point in future.
India is a very populated area, so if we were to have a region focusing on this place, there likely wouldn't be much quiet locations here, aside from areas such as caves, woods, and so forth. I'd imagine there to be a couple of cities here and there (with the most major one being inspired by Bombay), and everything else would likely be villages.
As far as Pokémon themselves go, I believe we'd find ourselves running into a lot of grass, rock, ground, poison, water, and fire-types. You know, groups that are more related to nature. As for others, such as steel and electric, we might be able to run into them on locations such as power-plant or a factory.