The difference between mechanical engineering and civil engineering is that mechanical engineering augments, enhances and enables human ability, whilst civil engineering along with architecture, enslaves, diminishes, and holds captive human capability.
Humans have legs they are meant to be mobile, not anchored to the ground like plants. There should be no need for passports, visa’s or permanent home addresses. Our homes should be detached from the earth’s surface and able to move to where we need to be, not hold us prisoner where we cannot survive.
If the world population was vastly more mobile, a lot of the worlds problems concerning deficiency of resources would be resolved. The only real checks we need on the movement of people is their health. Vaccination card or health card should only control movement, it should not stop the movement of people.
It is doubtful that freeing the borders between nations would result in a massive uncontrolled influx of foreigners. People don’t so much migrate between countries but migrate between cities. Is there is freedom to move, then people will be able to readily move from one city to another. Currently illegal immigrants around the world are really no better off, because getting into a seemingly better city only traps them in another undesirable situation. But once there, there would be seemingly no where else to escape to, as the paradise expected doesn’t exist. But if people can freely migrate between cities then there is a greater chance that they will eventually find the right place to be.
If the world is built around trade, then people need people. There is a minimum population for the system to work, and the population needs to increase in finite steps to allow increase in supply of goods and services. That is if the population increase is either too small or too small, then there will be a supply deficit, because in both situations the production facilities cannot be economically increased in size to cater for the population.
With fixed infrastructure anchored to the ground, the people of the world have to be like hermit crabs, and take up residence in, and accept the facilities which already exist. That requires shifting the world population to where they are needed.
If facilities weren’t anchored to the ground, then they could be moved to where the people are located.
It is a question to be resolved: is it better to move people, or move people and facilities.
There is no single answer to the question. Politicians no doubt would prefer t remain anchored to place with a captive population. Many people also would prefer to stay in the one place and have hopeful expectation that they can continue doing the same thing day after day, and generation after generation. Other people would prefer not to be trapped, and able to move to new locations and provide their services which are needed in the new location, but redundant in their previous location.