I had an idea strike me while thinking about this thread while at League. Why should the Gym Leaders limit themselves to just one of 17 game typings when the TCG forces 9 different types? As people already know, the TCG categorizes the 17 game types into the following:
:colorless: = Normal, Flying, Dragon
:grass: = Grass, Bug
:fire: = Fire
:water: = Water, Ice
sychic: = Psychic, Ghost, Poison
:lightning: = Electric
:fighting: = Fighting, Rock, Ground
:dark: = Dark
:metal: = Metal
This would also allow the Gym Leaders more pokemon to choose from so their teams aren't so easily countered and make pokegym really stand out as a place to go for gym league battles due to the unique type structure. Dual-type pokemon could also be under either type.
There is a tiny problem with my idea though: those with still only one type to choose from and there being 9 types instead of 8. Perhaps Dark and Metal could be combined under one gym and/or those gyms could be allowed more wildcards than the others. Just a thought.