Originally posted by Kirghiz
I was thinking ranked scrims too, but you're right it would be exploitable. In that case I would use probably GLB Tournament games and League Games. Using tournament data would be about the only way you'd get any usable cross league data to generate rankings from if you don't use ranked scrims. You could combine with this suggestion:
http://goallineblitz.com/game/forum_thread.pl?thread_id=4480443to have a free-flowing ladder system to encourage cross-league games, and aid in improving the rankings. A teams' ladder rank could even be included in their overall ranking.