Starters- it gets tricky because I feel like starting with starters from other regions will make you feel like you are in the typical region. Here are some suggestions I've thought of, Poliwag, maril, seedot, sewadle, magbi, vulpix. But if I had to pick a gen it would probably be sinnoh or johto starters
Gym types- Normal, ground/Rock, grass, fire, electric, water, flying, Dragon
Elite types- flying, poison, fighting, dark and the champion being a red like character with different types
Post-Champion areas- Maybe a forest where some of the Pokemon you couldn't get in map would spawn? There was a place like this in unova.