Debt agreements aren't required to be underwritten in every instance -- it's an entirely optional addition. If you want to see an example of a debt agreement in which there is no underwriter or middleman and collateral is trustlessly secured -- well, it's linked as OP :)

Oh this is interesting. In India, debt agreements have to be underwritten. Moreover, this right is a hard-to-get license that is granted by the central bank - Reserve Bank of India. Not sure what the regulations are in other countries.

Underwriting is a heavily regulated process in most countries with licensing requirements. You could claim that you do not underwrite yourself,so don't fall under regulatory purview. Interestingly your model will fall under the P2P regulations of India and China - where there are specific models where the marketplace does not underwrite, but risk is assumed by lender. Or - you have to make sure that the underwriters are regulated entities.

P.S. I run a lending startup in India. We primarily look at the Blockchain as a means to solve the credit history problem in India.