It gets better. If the pool uses PPLNS payouts they can issues ecash tokens for each hashrate share. These tokens have indeterminate value until the next block is mined. When the pool finds a block the value of the tokens is discovered. This forms a natural boundary to rotate the ecash privkeys and start a new epoch. Once the epoch is fully cleared the pool can publish proof of reserves exactly like your proposal. Mining payouts are 100% private, transparent, and verifiable. But wait, it gets better! Miners can sell their hashrate tokens immediately to buyers who value on-chain privacy. The buyers get a fresh KYC-free coinbase output. Miners get compensated for the privacy premium of mining rewards. But wait, it gets better! The pool can also auction off the rare sat at the beginning of the coinbase using sighash anyonecanpay. The auction proceeds flow directly into the coinbase, allowing all miners to profit from the rare sat premium. You don't have to believe in ordinals to profit from them. Again 100% private, transparent, and verifiable to the whole world. I can't stop thinking about this idea. DM me if you want to help build it.