Still dumb how LA didn't have non-hisui forms available for anyone other than Sneasel, who needed to be there out of contractual obligation thanks to Weavile beinga gen 4 Pokemon, and Alolan Vulpix/Ninetales because i dunno. Popularity, I suppose.
I'll be honest, I don't think those would actively add anything of worth to PLA. Fow SwSh and SV it makes sense since you can at least use them for online battles, but PLA being a self contained adventure kind of gives the og forms nothing to do. I feel like more than any other games in the franchise, PLA is about completing the region's Pokédex - would be kind of counterproductive to have 20ish forms to get that aren't even found naturally in the wild. OG forms would also have to either be Distortion-Exclusive (Which would absolutely flood distortion encounters with 20ish mons), in-game trade (which defeats the game's main gameplay of going into the wild to catch mons in the overworld) or be transfer-only (which also does that but as previously discussed doesn't really give the transfered mons anything to do)
As for Vulpix, they're apparently the official pokémon mascots of the Hokkaido region of Japan
So they were probably just tossed into the hokkaido-based region as a cute nod to that
With all that said, I fully expect SV to have all variants for a mon since none of the things that made those a bad idea for PLA apply to SV. So since we've seen Meowth and Pikachu in trailers, for an example, I'm expecting Alolan Raichu, Alolan Persian and Perrserker to at least be transferable