I liked the original proposition that the new mayor had for the city.
Give everybody the chance to move closer to downtown. Possibly even subsidize some of it with federal money (IF possible). If they can't, and if these people don't want to move? Change the borders of the city anyways and create several unincorporated sections of the city to be patrolled by county level officers and aided by county/local volunteer medical services. Developing this might take time but it's the only way you can let these people live and stay in their homes without having to relocate should they decide that's what they want to do. I imagine response times will rise dramatically but Detroit has to make tough decisions, the people living in these homes need to make those decisions as well.
If it's unsustainable, it's unsustainable.
And for reference: http://www.detropiathefilm.com/
Good film.