Alright, how about, the online league is in the form of a ladder? The season consists of basically, a period of time. The top 16 teams or players at the top of the ladder, when the season ends, qualify for the lan championships. In between seasons, the ladder is frozen. When the ladder resumes, everyone starts where they ended, except for those who went to the lan championships, who instead are placed in their lan finishing positions (so if you won the championships, you would start the season at #1 on the ladder).

People would play in the ladder, because it's the only way to win any money at the lan championships. Besides which, there should be money to win during the course of the season (in fact, every game in the top 16 should have some money involved). With all these ads in Quake Live, and the subscriptions fee's, and ads that could be in GTV/streaming-video, paying the high-ranking players should be doable. And, of course, if id really wanted to, they could deny everyone else the right to use Quake Live for their tournaments and leagues, thus ensuring a monopoly on Quake Live competition (and ensuring, if you want to make any money playing Quake Live, you have to go through their system, like it or not).