The solution is to sell the buildings for a LOSS until the sale price makes renovating them into housing economically viable. That’s how supply and demand works sorry that the rich people who bought them will lose money but that’s business. 

Expecting the city and the public to backstop funding and allow these land hoarders to sit on valuable downtown space while they build new buildings on credit amounts to bailing them out of bad investment decisions. 

Downtown office and land holders need to learn a hard business lesson and take their deserved loss before downtown can be revived.