While I like the idea of regional variants, I feel Alola made them too extreme. Stuff like changing Pokémon types entirely (Vulpix) I feel is more the realm of special phenomena such as Delta Types (from the TCG).
I'd like to see regional forms that go more for the sense of ecosystem fittingness and cosmetic changes than something so foundational that it should have been an entirely different Pokémon. Stuff like say the crests of Feraligatr in more tropical regions being flatter or less saturated in colour, so that they can hunt more effectively in clearer and better illuminated waters.
...Come to think of that, why not make the differences in sprite work from older generations into regional variants? Rounder Pikachu from flatter regions where climbing is not as important as being difficult to eat, darker and bulkier Feraligatr to better mingle in swampy regions, paler or darker Nidoran depending on the toxins they build up from their local diet, the shapes of Blastoise's canons fitting the hunting at different ranges in different regions, that kind of stuff.
That is something I would totes take as regional variants. Not "lol we are too lazy to create a new Pokémon".
