I think what I am imagining would be a feature of locktime. A set amount of payments would be associated with the cost of a good, So the mint can pay to pubkeys associated with customer wallets. I think this demands additional features in the e cash codebase. A P2PK with a fixed value associated with an inventory, Where the cashu nut does not expire until the transactions are all fulfilled and the 
token can expire. 

 Sorry the customer pubkeys can pay to an owner pubkey to fufill a token. 

 Each product can have a pubkey and you receive it as a nuts11 token can be filtered by each product. 

 Huh.