the signature of ecash is just a number, couldn't PoW be applied to that number (at a binary level) so you can pass a blind signer some data commitment (sha hash) and then the blinded signature can then be checked for leading zeros? by revealing the x secret of cashu, anyone can then verify the PoW by interacting with the mint and getting the same resulting signature with the same PoW. then you as a client/user determines the PoW needed and start hashing for a sufficiently difficult PoW using deterministic noncing. this is Proof of Work done for a certain pre-image given to a certain mint, meaning the mint made the computational cycles to find the PoW, the unblinding then becomes a way to see that data commitment had sufficient proof of work done by the mint (a possibly known hashrate), could this then be tied to redemption of job shares of a pool? or any arbitrary data?
I have no idea if this is accurate or correct and hope that nostr can help.