"Nope, sorry, your company's locating here would push downtown density past the limit, you should find a greenfield site on the edge of town and build something new there"
A hard limit on the amount of office space per square mile. You simply can not build any more offices. The market forces then will take care of distributing the office space accordingly.
If you absolutely NEED to have an office in The Downtown, then you will just have to pay $$$$$$$$$. Otherwise you'll have to rent an office in a nearby suburbian village center.
Kind of like we did cap-and-trade for sulfur emissions.
Maybe to ensure that the country is evenly developed, which would make housing more affordable across the entire country. The US is not even that bad - unlike many other countries, it doesn't have a true primate city[1] on a national level. I'm thinking of places like England, where the privileged areas of London (and the Home Counties), Oxford, and Cambridge are the only place to earn a decent salary, but have extortionate housing costs, while the rest of the country has much lower housing costs but such lower wages that people are pushed to migrate into the privileged areas, pushing housing costs there even higher. Densifying the cities would help to some extent, but construction tends to cost a lot more in these cities, and not entirely due to zoning, planning permissions, etc.
"Nope, sorry, your company's locating here would push downtown density past the limit, you should find a greenfield site on the edge of town and build something new there"
???