Migeru:

As lenders of last resort? That is still needed,

In Hong Kong it is not the Central Bank which fulfils that function because there isn't one.

Migeru:

As credit regulator/supervisor authorities?

A Monetary Authority - as in HK - would set the parameters/standards for credit creation.

Migeru:

As central clearinghouses for payment and settlement?

There is no need for a central counterparty aka single point of failure.

A mutual guarantee with a default pool managed by a service provider would do fine. eg P & I clubs in the insurance industry.

Settlements/netting of open bilateral credits requires only suitable software and algorithms. brent forward contracts settle this way on expiry by generating 'chains' and book-outs.

"The future is already here -- it's just not very evenly distributed" William Gibson