I am honestly surprised you did not put up there self-sustainable economic systems. Systems where people would exchange real goods and services but would not necesitate a central arbiter.

Think of things like Uber or Airbnb. I could theoretically imagine a system with the proper incentives between users, providers and a incentivised system of decentralized arbiters or oracles that could be self-sustainable. You would lack a central authority but they would all work within a framework. But the fact that you lack this authority could potentially make it un-bannable. It would effectively be a system of peer to peer transactions that could offer come form of settlement in case of conflicts.

Hard to pin down, but not impossible, I think.