>>49049718My theme would be going back to the basics. A coming of age story starring A Boy & His Dog (replace "Dog" with "Pokemon").
Grounded character designs, simple bad guys, challenging & intimidating gym leaders, one mean rival, one nice friend rival. Returns to the quasi-futuristic cassette-punk world of Gens 1 & 2, but with a 1950's-1960's aesthetic. Other aesthetic involves old school Americana, like apple pie, baseball, Converse shoes, etc. No shoe-horned legendaries (you have to search high & low to find them), no overly-idealistic evil team (they're just punks & criminals), no champion holding your hand (you meet him once before the end of the game). Also, after the first town, every route, forest, cave, mountain, river, tunnel & dungeon is a TREK, think like Rt 119 in Hoenn or most of Sinnoh's routes.
Gyms are based on strategies, like a Sleep Gym, a Fire/Grass Sunny Day Gym, a Water/Electric Rain Gym, a Toxic Gym where only Poison & Steel type Pokemon won't be poisoned, a Switch Out Gym, etc. I'd have it like a combination of JelloApocalypse's Pokemon Game & Crystal Clear, but with no SJW stuff.