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yeah, actually I was talking on skype about making a ladder tour for all gens ou a couple of months ago. Could have RBY as first week, GSC as second etc.
I might would've done 2 weeks each with top 4 from each advancing, or 1 week each with top 8. Then a double elimination playoff where it works like a Smogon Tour does where it alternates between the 3 formats.