Ok... so I may have messed up on my last post. I was thinking, at least one starter would be related to the region like with Hisui. However, that is not the case as none of the starter pokemon are Sinnoh in Legends. So I don't think a starter from that region would be a starter for a Legends game.
While I keep most of what I said about Unova and Kalos, I think these would probably end up being the better starters.
I am going to spoiler the lists to save room, but there is no actual spoilers within.
Unova:
Kalos:
_________
While I am at it, I kinda want to do all the regions, so here are what I think would be good for others.
Galar - I think since it is England based and while dragons aren't really prominent there, I think it would match better, it could even explain what pokemon was attacking the Galar Region. So....
Hoenn - With a Hoenn Legends, I think they could explore more about the meteorite that hit the land. We could also learn more about the Draconid People. Which I think would be closely related to Sinnoh and Galar. Possibly even Unova given it also has Regis. That being said.
I feel like Kanto and Johto would have to be together, given the fact they are right next to each other and share a lot of the same stuff. Their lore from what we know thus far, is very close together. In all honesty, Kanto has no ancient lore without Johto. I mean, we know nothing about Kanto's ancient past. There isn't really any ruins from ancient times or anything. And with both regions being so small, I think it would be wise for them to be together for a game like Legends.
Alola - As much back story as Alola has, I do not think it would get a legends unless they combined it with Johto and Kanto. The fact that it is basically persevered since ancient times and there aren't even any fossil pokemon. I don't think it would be wise to have it as its on Legends game. And if for some reason it did, I think Maganium, Swampert and Cinderace would be it. But I just don't think it would have a Legends game.