>>48375138> Hisuian DecidueyeThe entire point of regionals is to change a Pokémon to make it fit better in a certain environment, the Final evos we have now already work with the setting and Decidueye in particular fits the most. At least with Typhlosion and Samurott, the hypothetical regionals could make their inspirations more obvious and give them another type. Decidueye is already so obvious as an archer that any Hosuiam form would barely change. It can’t even gain a second tyoe because it has one (it could change the ghost type but to what). And if one is the starters isn’t getting a regional, no one of them will.
I’m not saying it’s impossible, I’m saying it doesn’t make much sense.