Yeah, we're seeing the first problems with that right now- newly uploaded bots progress faster than they should because they play against a more "diluted" pool of opponents than the oldtimers did.
We'll think of something.
I also think your alpha-beta bot is objectively better than the (currently) #1 bot.
Easiest thing to throw together now is a script which just feeds the whole game history into bayeselo as a bunch of fake chess matches, with the white move advantage set to 0. That's what was done for Tron.
