I would say the mint would mint onion-ized e-cash to users via a member, which we can call a teller, and that member can decrypt the outer onion and send to the user's wallet. The teller issuance protocol ought to necessitate some broadcast to the other members so they know it's been issued, such as making a decrypt request to an adversarial teller, and/or making pre-minted e-cash more like a withdrawal by the teller that gets credited back once properly issued. It adds some latency, but that's a low price to pay for the federation to be able to verify issuance.