I agree, I think both single signer (Cashu) and multi-signer (Fedimint) e-cash mints will play a big behind-the-scenes role in how open protocols work.

* A Nostr client could use a designated federation to shard payments to content creators, note amplifiers, routing relays, and in the future, storage relays.

* Cashu has potential for delivering payments to new contacts who may be offline or not have a lightning wallet. They can collect from your mint when back online or when their wallet is available.

* Mutiny’s use of Fedimint for offline LN payments is also a brilliant use case.