hey, idea of rating AI sounds very fun but I'm not so sure about the methodology. I mean rating them on how playing them "feels". There are some ladder players around 1300 that I feel rather comfortable playing and 900 that I wouldn't feel confident playing at all just because of their unusual playstyle and although I would still reliably win with those 900s, I probably couldn't rate them properly just after one game by "how it felt". If you really want to rate those AIs, maybe it would be optimal to also get them play lots of games against each other on multiple maps and see which ones beats the rest(similar way to how we estimate real players strength).
The tournament was very fun, thanks for organising it