A recent study from the Santa Fe Institute shows that cities are excellent systems – they are efficient social reactors and networks. As they grow, they make larger and denser social webs available to each participant, without any additional effort from the individual. The study does not suggest any diseconomies to scale and maximum limits.
Conceptually, then, the larger a city is, the better. This implies that the best design for humanity is to establish a single city that houses all of the World’s population – about 7 billion currently. To reduce extra-terrestrial risks from such a concentration, perhaps a second city can be established, at a location diametrically opposite to the first one. The second city, a mirror image of the first, could be left vacant for emergency use only. With distributed 3D printing, conventional manufacturing can be eliminated. Power production can be designed at mega scale with concentrating solar and wind farms away from the city, with efficient transmission back. Vertical farming may allow food production in close proximity. Excess power production may ultimately eliminate the need for farming, with instant conversion of power to food or direct consumption of energy instead of food.
With a single city design, most of the World can be returned to its original state. Such a system will have higher diversity and associated flexibility to mend itself after shocks.