I don't think a lot people would be averse to 100% working in the office if the commute was a fifteen minute walk. For most, it's the time, hassle, and expense of commuting that is a drain on their soul. Of course there are other factors, but in my experience, gathering at the water cooler and lunch with coworkers, etc., are sorely missed. Just not enough to justify hundreds of hours of my life in gridlocked traffic.
So, if they convert a few of these buildings to homes and parks that make living in the city affordable and pleasant, I think most people would be glad to use the rest as workplaces. Imagine a park and daycare for the kids only an elevator away. Eateries and shops in walking distance. No need to own a car.
We could have that if we get our act together. Now's the time.
TBF we are talking about unrealized gains. Their investments are worth more on paper, but until they sell them, the actual profit or loss will fluctuate. It would be an accounting nightmare to figure tax on unsold investments every year. I do, however, think capital gains should be taxed at the same rate as wage income.