I like Champions with teams that have more diverse typings, personally. I think it shows they build their teams to be as balanced as possible rather than because they have a passion for a particular type, which often matches the player (since most people either use their favourites or strive for diversity outside of monotype challenges or the like). Honestly I'd like the Elite 4 to be similar, use the gyms to show off types and let the Elite 4 demonstrate themes or styles? You could have a weather specialist whose choice of weather depends on your starter (Hail teams against your Grass starter, Rain teams against your Fire starter, Sun teams against your Water starter) or members with themes tied to the region (I'm not particularly knowledgeable about Spain/Portugal to talk about their culture, but in Galar for example you could've had a music-based member (yes Piers exists but he doesn't really count) or a nautical seafaring member). That would be a nice challenge towards the end of the game I think, plus you could keep the SwSh gym leader tournament before to test your mettle before the final bosses - maybe treat it like Victory Road?
As for regional variants, Kanto is definitely getting some more representation on that front in Gen 9 - I don't really mind this as I think after 25+ years some of the Pokemon there could use a new lease on life, especially if we're giving them regional evolutions like Sirfetch'd and Ursaluna! I think seeing some more Johto, Unova and Kalos representation within that would be nice too - Johto is also 20+ years old at this point whilst some of the Pokemon from Unova and Kalos are quite forgettable in their own ways? I think we could see 100 new Pokemon in Scarlet/Violet with 15 or so regional variants (regional evolutions not included since they'd be new Pokemon entirely) - 115 "new" Pokemon would be better than what we had previously I think.