I would like to avoid negative discussions. It is well-understood that micro-nations, city states, and isolated populations are rarely entirely self-sufficient and simultaneously prosperous. The great advances of human kind have taken place from trade and interaction, specialization, etc.
However, to be completely reliant upon others is foolish and risky. Some level of self-reliance and productivity is necessary for risk management of supply chain interruptions, and a completely sterile environment devoid of plant and animal interaction is unhealthy for humans psychologically.
Therefore I would like this thread to concentrate on what is practical, what is already economically proven, and what is theoretically feasible, and be educated and entertained by this specific subject along the way.