Thought: It's much easier to impose compulsory insurance than it is to legislate liability. So to say that landlords are held liable for the crimes committed by tenants is a major change of liability framework, but to say landlords are required to carry insurance in case they have thug tenants, that could be even a zoning bylaw...
So you could take a place that's currently zoned single family, and propose a zoning law that apartment buildings are legal, IF AND ONLY IF they are insured against tenant criminality. That way that area is able to urbanize without becoming a ghetto.
@cjd Sounds good, but municipalities change zoning all the time, at least in the cities. As far as insurance specific to crime, that would be very difficult to get. If you do, it would be very expensive, and then they come up with excuses of why they don't cover it. Then drop you. Further, if you needed a loan for your project, the banks hold you accountable for not having insurance, and can call in the loan. 