Although I hate asshats as much as anyone, I don't think a global ban list would work. Individual servers have differing rules and regulations on kicking/banning. For example, some servers do not allow run n gunning and others do. Some are more lenient than others on matters of tking, message spamming, player abuse, etc.
Btw, the last time something like this was proposed it was locked so....
....in before the lock! (maybe)