Well, I would agree with all of them, except maybe with Registeel representing the cities, since those Pokémon were created long before modern civilizations.
However, as an interpretation of their meaning, I find it quite reasonable, with each Regi representing different parts of the continents, and their leader, Regigigas, being the one who crafted the continental landmass into what it is today using those 3 elements.
Sorry, I tried to send you a PM awhile ago, but it never sent I guess. I have quite a few I need, you just need to pick from these: Ice Beam, Thunderbolt, EarthQuake, Gyro Ball, Calm Mind, Toxic, Stone Edge, Explosion, or U-Turn. Not the eaisest to get, I know, but they're what I need. since it's just a weedle, you can choose one of the above and send it on a Magikarp, if you have one.