Ninetales and Arcanine play similar positions in Red and Blue, so it got me thinking... If that's true, why not differentiate them in Sun and Moon? The result? A Fire/Water dual type Arcanine! It would make a bit of sense according to the lore too.
While this image comes from DeviantART user Viper-mod's Pokémon splices, I actually came up with the idea of a Fire/Water Arcanine from an old Pokédex entry from Pokémon Stadium:
A Pokémon whose beauty is legendary in China. It is said to run gracefully and lightly, as if it were flying.
While Arcanine doesn't literally fly, maybe Arcanine in Alola developed the ability to fly as a means of getting from island to island by taking on a lighter, perhaps more gaseous form (i.e.: steam)? Considering the number of hot environments Alola's bound to have, I'm sure at least one would be able to make this evolution a possibility somehow!
That, or I'm literally blowing steam...