If you do fidelity bonds for sybil resistance, there's not much that distinguishes it from JM, except for a nostr relay orderbook instead of p2p gossiping. That does protect IPs (if you dont use tor) but I would still say it's just a marginal improvement. The point of zerolink is not protecting IPs, it's to break all deterministic links using equal output coinjoins. I actually see a future in which JM or your proposal could implement it. It could be something like an "advanced coinjoin market pool" that would require a previous tx0 type transaction that guarantees the utxo to mix is compliant with the pool amount.