That's the kind of thing that would need to be automated imo... It's just not practical for me to try to manually create a ton of 8 person tournaments. It's also something that could be handled by an individual if they're passionate about it.

Make a proposal and ask for some seed funding for the prize pool with a gameplan to recoup and burn the DEC. My strong suggestion would be to ask for Rebellion packs with a gameplan to burn 4,000 DEC per pack the DAO allocates to this idea.