Alolan Raichu, Marowak, Exeggutor
Galarian Weezing and Mr. Mime
They keyword you missed was "alt", as in alternative.
All the Pokemon you mentioned are Regional Variants of existing Pokemon. When I say "Alt Regional Evolutions" I mean Pokemon like Perrserker & Rungerigus; they're not Galarian forms of Persian or Cofagrigus but rather take their place for the Galarian forms of their basic stages.
The point I was trying to get across that, since the Starters aren't native to Hisui, it wouldn't make sense for them to get a Hisuian variant (aka no Hisuian versions of Dartix, Decidueye, Quilava, Typhlosion, Dewott & Samurott). So they would have to be new branches, new cross gen evos. BUT, working off from what we've seen that GF don't want to do those anymore, the only way to do this would be connecting the new cross gen evos with the Regional Variant mechanic. Eitherway it would be expanding upon the definition of what is a Regional Variant.
Edit a few minutes later with some more thoughts:
I'm pretty sure GameFreak's aversion to "new evolutions for old Pokemon (not including entirely alternate evolution lines e.g. Galarian Farfetch'd)" since Gen 5 is because that's when they added Eviolite, so now cross-gen evolutions are a backwards-compatibility break -- and we know how weird Gamefreak gets about backwards-compatibility for evolutions and evolution methods. (Which is why the only true cross-gen evolutions we've gotten since then are for Eevee, who... already had evolutions at that stage, so its Eviolite boost at the Eevee-stage wouldn't have changed.) This factor does not matter at all for the Legends starters, who already have full evolutionary lines, and tbh this is the only reason alt evolutions should be considered possible for them.
This is also why it's 100% possible there will not be a Hisuian Scyther: because Scyther already has an evolution in Scizor. Basculegion and Wyrdeer, though, would need a Hisuian Basculin and Stantler, under this line of thinking.
I don't think that's the reason (like the Galarian counterparts that got a new evolution still have the same BST and would be getting an Eviolite boost; just the normal counterpart wouldn't). I think the reason was more due to the massive backlash they got from all the Gen IV cross gens they introduced, many whom designs weren't liked or criticized for taking the different in a different direction. And you know how people get protective with their favorite Pokemon, so many whose favorite Pokemon were say Magmar, Piloswine, & Rhydon may not have been too pleased that they're no longer fully evolved Pokemon but instead they evolve into Magmortar, Mamoswine, and Rhyperior. Regional Variants & Evolutions gave them a way around all of this. They wouldn't touch the normal form thus fans of that Pokemon would be happy & they can not only experiment giving a new twist on the existing Pokemon but now can further their evolution line.
And not sure I follow your logic with Kleavor. Because there's Scizor thus there's no H-Scyther? Perrserker & Rungerigus would like to disagree with you on that.
I believe that Wyrdeer is the normal Stantler evolution. Just look at the guardian's pants.
Just saying, normal Stantler probably exists, Hisui may just have a special breed of them. Or maybe H-Stantler doesn't look all that different from normal Stantler in a way that the clothing pattern is able to hide. Alolan Diglett & Geodude only have slight visual differences that is extra parts of their design and isn't a "major" color shift.
Also, looking at the Stantler on
Mai's pants leg, there is this odd little "spike" coming out from its back (and its eyes have a heavy black mark marking and eyelash). Even if you discount the eyes has a design choice, it's odd for them to have added that spike on its back. Also, we don't get a full image of the Stantler pattern, notably the top of the antler is cut off.[/quote]
