I do agree that incentives (and dis-incentives) are typically superior to other forms of regulation.
For example, a higher property tax for unoccupied buildings (or a tax break based on occupancy) might help get things moving.
Though, in the case of commercial property, that might not be enough. A root cause is Bank officers handing out loans like candy and basing the value of the collateral property on "anticipated rent". The owners are now afraid lowering the rent will trigger a re-valuation and the bank demanding repayment or starting foreclosure. Meanwhile, those officers know of the situation but don't want to rock the boat until they can get promoted far enough away not to have it come back on them , or better, make it to retirement first.
In truth, forced re-valuation is most likely the only way to break that log-jam at this point. The market isn't going to grow enough to actually make those turkeys rentable at current asking.
For residential, a grace period on some of those rennovations in exchange for actual occupancy may help.
Per buck you get more computing action with the small computer. -- R.W. Hamming