I looked at the idea of charter cities and special economic zones as models for urbanization. I think it'll be easier, faster, and less error-prone if we were to strengthen the movement towards greater rural governance and build up the rural areas towards the new designs.

India, for example, has a political architecture with a strong center and states, and weak districts, cities, and villages. It also has existing political support to improve villages, and that movement can be amplified.

The "Cloud Countries" idea in https://1729.com/how-to-start-a-new-country/ is cool. It's also orthogonal to the physical footprints that are the focus for sustainability. A person can be a LARP in many cloud countries, and also physically resident in a mud-world country so these don't conflict.