Another suggestion for more statistical realism. Population growth dynamics.
The "top density" CANNOT just keep rising, especially at a constant rate. This carries the insinuation that eventually, every building is a burj khalifa, and that ONE is built every month, at zero cost to the economy. Also, it assumes that the productivity per worker rises at the same rate. In reality, 20 Burj Khalifas will not result in a more productive citizenry as it is all very compact and there will only be traffic jams.
The productivity of a nation is not just about citizen count, but accommodating infrastructure. It's not right to have the whole map turn PURPLE and for small zones to "DIFFUSE" Cities are easier to build than just expanding small towns. Small towns should turn into city zones, instead, they diffuse until the whole map is "FUZZY and BLURED" with no zones that are cities.
Better population growth modelling please. (more realism) and better productivity per citizen assumptions. (trend line relating to concentration of people) (For median worker productivity)
Less diffusion and more accurate population growth where cities still look like cities and where towns can turn into cities. Definable zones, not just blury goo spreading but something that looks like actual infrastructure development.
maybe also have Industrial zones for mineral extraction and factories, residential zones for population concentration, agriculture zones for food. Some land that is too hot or too steep (Sahara and Himalaya) would NOT be able to have cities without spending 100,000,000 times MORE per square meter of infrastructure, (It's not possible to build new york city on the Himalayas in 2 years)