Aha, I get what you are saying. Using a different UTXO than the channel output as the “anti-spam cost”.
However, I’m not sure if it give us anything (in a non-ZK scenario it obviously could):
- Since channel counterparties have to create a multisig output in order to open a channel between them, you already have a utxo available for this purpose. (if we wanted to allow channels not backed by a real utxo this would not be the case of course…)
- Channels are often created between non-trusted parties. Who would put up a utxo in that scenario? If both had to that would be less scalable of course.