Here's what I think we should do - for X/Y anyway.
We each take a team of two. Only walk in with two. Register them with Polar.
A bracket is made of the candidates. Matchups are determined. START FRESH; some haven't had any chance to battle yet or been challenged, and in my case, I still don't know what the hell I'm supposed to do.
From there, a double elimination takes place. Lose twice, you drop out. Each battle involves those two Pokémon. From the results of the bracket, Polar can decide who to have as leaders. Optionally, a "play all" format can take place; everyone battles everyone else once.
Of course, Polar has the right to either let the brackets decide or to overrule and choose someone as well. This may be if someone was playing with a weaker team and still won a match or two that shouldn't have been won due to skill, or so on. This isn't a winner takes all thing, after all; it's a Pokémon League.
Also, using overpowered Pokémon should be discouraged. IV breeding is fine, but using Megas or trapping styles should not deter someone's candidacy. If someone routinely sweeps everyone with a Mega Kangaskhan, for instance, that doesn't make them the best battler. Polar has a right to reject a team for this format, IMO.
