One "Simple Fix" for cities, albeit with limited scope: Force your Planning Commission, Zoning Board, etc. to keep track of the vacancy rates for commercial space. Then use their powers to strongly discourage the construction of yet more vacant commercial space. And/or renovation of such space to other uses.
EDIT:
- Please do not assume some trivial straw-man implementation of this idea. That includes City organization being hopelessly corrupt or incompetent.
How would this help? If the existing operators refuse to lower rents and leave their spaces vacant then under this scheme no one else can build new spaces which rent at lower rates. You would just be stuck with vacant properties at above-market rates.
This policy would backfire greatly. For one, if I want to keep a competitor from expanding into my town, I'll just lease some commercial space and keep it vacant. That way they cannot build in my town.
That is a bad answer because it invites too much power to those commissions/boards. They already have a lot of power which they abuse (in places) to not allow things they don't like that would be good for the community.
EDIT:
- Please do not assume some trivial straw-man implementation of this idea. That includes City organization being hopelessly corrupt or incompetent.