I think if you REALLY want to do round robin pools, you have to cut the numbers by half or something, just because 18 people is too many. There's a valid argument against brackets but IMO it's the most efficient anyway.
Check out my Youtube channel for high level Allstar matches and eventually other video game gameplay. http://www.youtube.com/user/dabuz18/videos?flow=grid&view=0
And is only this "qualifying" round bracket, or is the whole thing bracket?
"The Dirty Casual"
Once you are pastafied, you can move up and down the leagues; I woul never be so cruel as to not let players who have advanced in their skills try to make their way up the ladder.
The top 8 of the Alfredo and the bottom 8 of the Marinara compete in a double elimination bracket to try and either move into the next leagues, or stay in their own. Same for the Pesto and Alfredo.
The Bolognese league is just a qualifying bracket. I had no way to seed people for the actual league and needed one, so I created the Bolognese League.
Did I make sense? (I have been told I am a tad confusing at times.)