Without delving into the specifics of any plan (noting for the record that Democrats were the first to announce a plan), I've learned a little bit about how people understand urban planning, and my take is probably not very typical.
My experience is driven by personal history as much as it is by theoretical studies of the failures of micromanaged, paternalistic design as suggested by people like Le Corbusier and dissected by Jane Jacobs (among others).
I've seen how sprawl can destroy a beautiful area, Lawrence being a classic example. The city has about doubled in size over the last 10-15 years, and most of that growth is new construction out west, along I-70 and K-10, toward Topeka. That's fine, but the people living in little planned communities aren't getting the Lawrence experience, and that sort of development takes a lot away from Lawrence. To sustain that sort of development – probably the most common sort of new construction in America – new strip-malls are built, roads are widened, and the cohesiveness of Lawrence as a whole diminishes. Every house looks the same, unlike the quirky Victorians around downtown, or the less elegant but equally unique houses of East Lawrence. Indeed, the houses in west Lawrence don't just look like one another, they look like houses any suburban development in America. The strip malls have the same chains that occur nationwide, the houses look the same, and it isn't Lawrence, it's Levittown. In the process, Lawrence loses the beautiful farmland that once surrounded it, and a belt of low-density, inefficient sprawl grows until it links Topeka and Kansas City. Blah.
I've also seen neighborhoods like Jane Jacobs writes about. The area where my mother grew up in Brooklyn has a nice mix of duplexes, apartment buildings and houses. Every few blocks there's a little commercial district, and stores she visited as a child are still operating here and there. These are locally owned businesses, like so many of the stores on Massachusetts Ave. in Lawrence. Money stays within the community, people know each other and take care of one another. Children grow up together, mothers watch over one another, and the subway is always there if you need to run some errands.
New York is no panacea, of course. Harlem, like the South Side of Chicago and other neighborhood victims of redlining, spent many years in self-reinforcing poverty. It's an area full of beautiful houses, but also gangs, drugs, projects, and violence. The reasons behind the historical poverty of Harlem, like the story of its recent revival, are too complex to fit into a blog post. Racism and positive feedbacks of poverty explain a lot of that, but not all. After all, the area where my mother grew up was largely a community of immigrants, who start off poor, but somehow the neighborhood and its inhabitants did well for themselves.
The other factor that helps explain the poverty of Harlem as a neighborhood is best exemplified by the fact that, for many years, there was not a single grocery store in the neighborhood. To do shopping, you had to ride the subway or take a taxi. The bad aspects of the neighborhood scared off potential investors, and the lack of economic opportunity promoted those same bad aspects. Clinton-era economic policies raised the income in Harlem while reducing crime (credit for that gets split with Giuliani). As a result, Fairway (a great store) opened in Harlem. Harlem residents started renovating the beautiful old brownstones, reinvesting in their community. Harlem is certainly not a full-blown success story, but it shows how certain interventions can benefit society.
These anecdotes (I have more from Chicago, but you get the idea) illustrate points that are ascendant in modern urban planning, at least according to my sources in the urban planning community. One important idea is mixed-income communities. Concentrating poverty, the philosophy behind projects like Cabrini Green (RIP), failed because it drives away businesses. Providing mixed income housing in a neighborhood ensures that there will be a local economy that lower income residents can rise up through. It ensures that schools in poor neighborhoods aren't discriminated against, that crime isn't ignored in poor neighborhoods, and makes it easier to do Giuliani-style "broken window" policing. After all, if there aren't any "poor neighborhoods" those disparities can't grow too large.
Another point, one made very clear by Jane Jacobs, is the importance of having local commerce. Local commerce has many advantages. Jacobs focusses on the social aspects, that it encourages community participation especially. The economic rationale above is another argument. The modern interest in sustainable development is another argument. If a decent commercial district is within walking distance, you can drive less. Less driving means cleaner air, clearer and safer streets, and cheaper gas for everyone.
Deregulate planning for an area and you'll see concentrated commercial districts and concentrations of wealth and poverty in different areas. I don't have data on that, just back of the envelope calculations, so prove me wrong if you can. Since that's exactly what we don't want, deregulation isn't the best plan. You have to enforce mixed income development, you have to zone small commercial districts throughout the residential neighborhoods. Doing otherwise kills the neighborhood.
So, my plan for No Man's Land would look like this. Impose strict controls until people get used to the arrangement. They'll notice problems: commercial districts that aren't clicking, low income housing that sits unoccupied or expensive houses that won't sell. That's when you start looking for people to offer new ideas, and when you start cutting regulations back. Inertia and experience will preserve what works, and new ideas will blossom. The regulators can keep an eye on aggregate trends, and if businesses/wealthy residents/poor residents are fleeing an area, it's time to sit down with the stakeholders and figure out what isn't working. Would an Enterprise Zone help? Should the commercial district be moved a block over? Is there a crime problem scaring customers away? The government can identify the problem and apply appropriate medicine, which might be deregulatory.
It's a plan that would work, a major advantage over Bush's plan.