I have always thought that the best way to tackle lack of housing in developing countries (e.g. India) is to work on the supply side. I mean if we could do something drastically to reduce the cost of construction and not rely on near impossible land acquisition process in some countries. The best alternative is a project like above made with some advanced future materials and constructed near the coast. Solar panels , desalination etc could be used to take care of part of the energy and water needs (these are the two biggest problems). Also rapid construction kind of the like seen in China using rapid assembly of parts on site can be very helpful. I really think this would be the most important solution that would make the world more equitable and sincerely hope something materializes within 20 years.
10x cheap, 10x less land, energy from renewables etc.