Most of my favorites are already thrown together as collections! But if I had to think of one... Imagine they put together the original Pokemon games from Gameboy, Gameboy Color, GBA, and DS and merged them into one big "collection". Like how Gold/Silver had the Kanto region after you beat the Elite 4. But in this version, you choose a starting region, then post last gym badge of that region you decide where to go next. Additionally, all the same legendaries appear in the game. Basically it would be just like Gold/Silver, except adding even more regions. Maybe giving you the option to continue leveling your pokemon or "reset" their stats at the base starting level for additional items or stat boosts.