So far I've only seen two basis for competitive Pokemon, one being Smogon/PO's usage based metagame and the other being PokeBattle's currency based metagame. Are there any other types of ways to battle that exist or that people haven't shared?

My friend pitched me the idea of there being a rotation type of meta, where 200 - 300 Pokemon would be thrown into rotation and that would be all you could use. It wouldn't be random because otherwise you'd end up with a metagame where one or a few Pokemon have no good counters and go on a rampage for months. I think it could be pretty cool.