If there's a fear that lowering rent would cause a problem (by letting others demand the same, or by lowering the assessed value of the property), what we need

If there's a fear that lowering rent would cause a problem (by letting others demand the same, or by lowering the assessed value of the property), what we need is model "turn-key" regulations to let them put the land to use without touching the shared lies. "Yeah, this normally vacant 400-square-foot unit in the Junkie District is worth $8250 per month, but we're donating use to a local non-profit, and when someone is ready to spend $8250 per month, we can boot them with X days notice." Plenty of groups (budget-constrained charities, maker spaces, educational programs, hobby organizations, political groups) could make use of idle retail spaces, even with the weight of a "we can drop a 30-day eviction notice on you at any time." And then when people walk down the street, they see "Oh, it's the Libertarian Party HQ and the local woodworking club's workshop, what a vibrant neigbourhood!" rather than "Here's a vacant store and you can still see the outline from the sign when this was a Fazoli's!"