If we had someone who could…
If we had someone who could act as an honest Oracle, we could make an AMM for this event on nostr using digital signatures, and on-chain commitments. People could bet on the team of their choice, and the odds would adjust according to how much is staked. At the end the contract pays out to all the bets made. However, you you need someone impartial to report the winner of the tournament. If the wrong winner is called the funds would go to the wrong place.