Have you looked into using the Interledger Protocol? It's the most advanced evolution of the concept I know:
Also, how do you propose to grow this network? That always seemed like the hardest part to me.
Great honor to get this message from you, I'm a great fan!
> Have you looked into using the Interledger Protocol?
Yes. It contains some things that I don't agree with. For example, I believe that the timeouts they have on the transactions are not secure. I also don't like that it binds users to the domain system and the traditional certificate hierarchy.
> Also, how do you propose to grow this network? That always seemed like the hardest part to me.
I'm not sure yet. I agree that this is a very difficult question. I might need some help.
Meanwhile, the debt idea is resurfacing on top of blockchains in the form of lightning payments. You can transact quickly via debts amongst a network of peers that settle their debts back to the blockchain for backing.