I've been thinking about this, and I'm curious how well a tourney would do.
The main reasons that pump has been thriving here are:
1. The Relaxed Attitude
2. It's fun
3. It's cheap
4. The Relaxed Attitude

A tourney has the potential to disrupt several of those. That's not to say that a tourney wouldn't work, it also has the potential to be great, and a nice change of pace.
But if I were to organize an event, I would try and stick to what everyone has loved about pump. Also, if we're "old school" then let's have an old school type of event.
Cheap entry, prizes are small trophies of some sort and bragging rights. Have a raffle at the end with some prizes that have been donated.
Which ever field hosts this, isn't going to make any "real" money from it, they should be doing it to promote this type of paintball.

Other things that could be fun, is DRAW teams. Everyone shows up and teams are drawn out of a hat. Keeps it fun and un-stacked. I've been at events like this. Makes it interesting, keeps a relaxed attitude and has the potential to make new friends.

Just some random thoughts...