I think we have a lot of data but not enough experimentation, the data so far indicates mega cities are efficient economically but only until the social conditions within degrade the whole society. I think a size constraint might be a good simple solution, but I think more technical solutions are worth trying so that we can massage and finesse the problem. I think the core of the issue is economic pressures induced largely by megacities and the moral decline we see associated with population density growing over time that is correlated to birthrate decline. My solution is to try and engineer village and rural lifestyles back into society. The simple practical portions are cut waste people that can be cut easily to reduce housing demand and cost, namely illegals and non productive non citizens, migrants need to earn twice the median income to get citizenship if this globalist idiocy is even going to halfway work(it's obviously about white genocide but my suggestion mitigates that intent and is palatable to normies and leftards) so reduce housing pressure and build new housing in the pavement wastelands we call shopping centers convert these shopping centers into dense mixed use housing and business developments designed to be walkable and comfortable facsimiles of european villages with parking decks at the corners, local businesses keep 70% of every dollar spent within the local community as opposed to 30% at big box retailers, wealth preservation is important in mitigating losses to reduced efficiency. These comfy villages locked into cities if kept ad upper middle class housing will make sure to produce offspring that are moral as opposed to the scant but uneducated barbarians predominantly produced in big cities today, my suggestion is that whites dress up like vikings and raid bigbox stores in their area during riot season and then put on their best duds and talk the city council into making villages out of the abandoned lots. I have a concept for a new model city but it's really just a compression of lifestyles for the efficiency of propping up wealth and morality engine in a rural to sub-rural population, essentially a circular town that has a staggering reduction in population density every block away from the central block. The goal is to have a town with ~35k pop and a single skyscraper that mostly relies on 1-8 acre plots in the outer rings to be self sufficient and produce moral children to take over the homes and farms and fill the denser zone and spill out into the old cities as a way to spread/maintain morality. There is also an education reform concept I have which pairs with this. But the gist is womens work is in the home and with new technology that means women need home business skills along with home maker skills and men and women both need agricultural skills and modern technology skills.