KurowaSan, you are a genius!!!
Seriously, i couldn't have done that much research.
Okay, now to comment:
SHIMANE -
The Izumo Taisho would most likely make an appearance in the game (the Scorched Slab in Hoenn is actually based on the cave where Amaterasu, the sun goddess, hid herself.)
TOTTORI -
I like the idea of Tottori Sand Dunes as a desert, and i like the idea of a ground-type gym as well (the last ground-type gym was in Kanto!)
Since Daisen is the highest mountain in Chuugoku, it most likely would be added. But i'd rather leave it as a volcano, for the fire-types to live.
And there could be a contrast between the volcano and cold mountain, like fire/ice, with the town of Tottori between them.
YAMAGUCHI -
I would say the Akiyoshi Plateau is the Elite Four place (just because 'plateau' is also is in Indido Plateau), and Akiyoshi Cave as Victory Road.
HIROSHIMA -
This city would obviously would be added. I was thinking for the gym, a Flying Type, because there was this girl called Sadako Sasaki who developed cancer from the fallout from the atomic bomb. She decided to create 1000 paper cranes because it is believed that folding 1000 paper cranes would grant you a wish. However, she died at 12 years old (according to the Hiroshima Peace Museum, says she finished it but continued folding more). She has her own memorial.
OKAYAMA -
Okayama city could the the city in the background of that bridge image. And because it looks polluted, maybe a Poison-type gym.
KAGAWA -
I would think Megijima could be the cave image with the electric rocks. I don't know why but maybe the ogres of Oni island could be creating it.
EHIME -
Agree with the Power plant idea.
KOCHI -
I would think Shimanto (a town in Kichi prefecture) should be the starting town, as it has one of Japan's cleanest rivers, and the starting town image looks... clean?
That's the only connection i'm getting. It's also on the southern tip.
Then Kochi town would be the next town over.
Anyway, your ideas of the locations seem more linear, storyline-wise, and mine seem more scattered.
I was going mention some Shinto myths about Izanagi, Izanami, Susanoo, Amaterasu, Tsukiyomi and Orochi, and relating them to possible legendaries, but i don't want to speculate too much. I'll wait in a month or something, til new info comes.
And looking at the city map, i think i can see 3 alleys in this city. And there seems to be an interactable building at the end of the clip, the stone-coloured building. It looks like a department store.
I think the city turns round back north so all exits head north (i think there's two exits, but i can't be sure, seeing the map).