The problem with that is not the changes brought to the metagame. Yeah, those changes would be desirable and probably would make the metagame better. But that would cause a big perception problem. People react much stronger to changes on the existing metagame than to additions to it. Right now, what we do is what would happen if Nintendo revealed another pokémon: It would be added to the already existing pool of pokémon, but the core mechanics would not vary. That'd be the equivalent of discovering, say, Shaymin when Nintendo released it, in the case we didn't know about it previously.
What you propose is a change as radical as the one that happened from GSC to RSEFRLG: Changing a lot of movesests, etc. People need a lot of time to get used to changes made by Nintendo, who are generally accepted, but I doubt they would take the patience to get used to our changes.
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