Re: There it is
"More subtly, employers should be looking at the possibility of replacing the city-centre ant-nests with smaller suburban workplaces for those who can't actually work from home for one reason or another."
Precisely. There's no need to have the art department bang alongside accounting. Functional units could be housed in smaller offices or have space available to meet together in different places if many of the staff work from home. If the senior management wants to be on the 40th floor of a downtown high-rise, no problem. They could even have access to CCTV that lets them virtually wander through different offices "to see how everybody is getting on".
With so much outsourcing already going on, companies are already physically divorced from aspects of the things that go into their products and services. If they have staff that don't need to be in a company controlled physical location, having them work from home could be a bonus all around. I work for myself now, but I've had a better home office than when I held an outside job for years now. My electronics bench is also better equipped than where I worked building rockets. If I want to have a creamy chicken, mushroom and garlic pie for lunch (heavy on the garlic), I won't have my colleagues whining about it. (great recipe from John Kirkwood on YT, btw)