Yes, I've thought about this stuff before. Reputation systems are good for lots of little transactions, but there is a subtle but important problem with this approach.

First, decentralization always breaks if the cornerstone of the system is trust in individuals/nodes/people. That's exactly how the banking system came about. People with more and more money, and more and more power, get more of the money and power because they're the only ones you trust to keep your money. People's trust concentrates in those "nodes". This is what we have to avoid in our P2P solution.

We need to make it so the trust is in the protocol itself. This requires public verifiability of transactions.

It's good that the contract is customisable, but if that ends up meaning that we only transact with trustworthy nodes, we get centralization.