At this point, I'd have to say evacuate all the remaining citizens, scatter them around the country, send in robots to do the dirty and dangerous work of bringing all the infrastructure up to par and keeping out anyone who wants to go in and make trouble, create DetroitCoin to pay off the debt (LOL, right?), wait ten years until everybody kinda forgets what was so wrong with Detroit in the first place, and then sell off all the properties to the highest bidder and let Detroit start over.
Good idea. But, it would be easier simply to move to an area about 10 or 20 miles away, and start over. Leave Detroit kinda like a Michigan "Chernobyl" so that we all remember the kind of meltdown that happens when Democrats get too much control.