I think this game needs an active hand in the economy, run by the dev team. Someone who understands economics and monetary policy. Think Federal Reserve in the US economy. Discount rates, reserve requirements, buying/selling. Even if you don't agree with the Federal Reserve, it's an integral part of the US economy.
Especially if people start forming 'banking' organizations. None of this works without a backend system to support it. It sounds great and looks good on paper, but if you can't enforce liabilities owed from one another, it all falls apart.
