Regional forms are variants of some Pokémon, yes. Those forms are, in some context, new Pokémon with new properties (for example, different evolution method like Alo-Sandslash). And this can have some interesting features:

> Some variant forms could have Mega but the original form doesn't, or vice versa. For example, there could be an Mega Alolan Ninetales (Alo-Ninetalite) and don't Mega (Default) Ninetales.
> Some Pokémon with multiple evolutions could have a variant form that cannot evolving in one of those evolutions (for example, Alolan Gloom couldn't evolving into Vileplume)
> Like as the last point, some Pokémon could have an inexistent evolution. For example, an evolution of Alolan Jynx.

Have you ever thought about the different features that could have the regional forms? I hope GF knows how to take advantage of this.