Wouldn't such an exchange be a good use case for a smart contract? It would make it very transparent, if the exchange is honest. As a history of all bids, payouts and judgments would be recorded on a blockchain. It probably also would do away with the KYC, so everybody could participate. And nobody would have to give away their private data. Thinking about it ... if the smart contract would let users post new bets as…
You could even have trusted middle-men that collect a Fee iff ambiguity is discovered and an appeal is wagered against the escrow.
I'm sure it exists and got rugpulled already.