It's interesting as a thought experiment, but it assumes that all decent plumbers would be conducting their business in a Chinese-owned Crytocurrency (Bitcoin),

It's interesting as a thought experiment, but it assumes that all decent plumbers would be conducting their business in a Chinese-owned Crytocurrency (Bitcoin), via a website registered in Libya (ly) and hosted by the Russian mafia, rather than just coming clean and paying their damn taxes. I have a creeping suspicion that you might be a sociopath. (edit: not meant as an insult. We tend to project our morals and biases onto other people, and the situation you're describing hinges on all plumbers and all clients being sociopaths interested only in their own benefit.)