I think the best idea is to create Urban parks out of the low density neighborhoods, and once you take out the bad parts hope that the land will be in demand again 20 or 30 years.
The whole 'city' is 'bad parts'. And it will never be in demand again because it is an urban wasteland.
I'm curious. Have you actually ever spent a substantial amount of time in Detroit? I haven't but a lot of people I know who have lived there like the place. I've interrogated them about it several times because my assumption was it was a bombed out wasteland of little worth. They tell me its actually pretty cool and they would move back there. These people were all professionals with graduate degrees. They were white and black. I dunno. I just don't think that place is the 100% write off we've been led to believe.
Look at Google Earth maps, and you will go, oh sh**t...
Before I opened this thread I thought Detroit was ed, but then I decided to look at google maps and i realized it's pretty much FUBAR'd. Like you need radical solutions for all the empty low density populations, urban gardens sounds good, but I think creating parks/potential recreation areas will make the land price surrounded by that go up a lot.