New Regional Gimmicks
-Pokemon type swap. If a pokemon is put in a specific pokéball while holding a particular stone, it's typing (or primary typing if it is dual-typed) will change temporarily, making is more like a mega-evolution than a regional form. For example, Liepard can be type-swapped into a pure Ghost-type. However, not all pokemon can type-swap. I imagine that there would be an in-universe explanation for this just like with mega-evolutions.
-Almost all gyms are dual-typed, meaning that the gym leaders don't specialize only in a single type.
--Odd keystones become crucial to find and defeating the evil team due to them hosting Spiritomb, a pokemon that is going to be used by Team Chaos in their summoning of the legendary.