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The only types I didn't mention were bug/poison types, so here they go:
Like I said, there should be at least one big forest area, so that means bug types. Usual Fluff aside, I think only worthy bug types should even be found, nobody ever sticks with butterfree and that other nonsense you find early on
Heracross, Grubbin, Illumise and Volbeat(Again, Double Battles), Pinsir and Maybe Buzzwole(Legendary) Could be good Choices. The token Fluff could be reserved for Vivilon and Ariados, and only if you find the game area early on. Joltik, Dwebble, Skorupi, Durant and Larvesta could be found in the desert areas, maybe an araquanid in the oasis areas
As for Poison Types, do people even use those, again? Arbok and Seviper depending on your version, and Garbodor in city areas. Mt. Battle could also have wild Weezings, any industrial area could also have a muk(Alolan or regular, maybe with former having a lower encounter chance)