There has been all sorts of beautiful renovations downtown south of Market Street, but the area continues to lack something that will make it a truly vibrant neighborhood. Here are some of my suggestions.
First of all, while they should not necessarily be eliminated, the entrance and exit ramps onto the elevated lanes of Highway 40 are intrusive, ugly, rapidly deteriorating and most importantly, they waste space. When the rebuilding of these structures occur, they should be reconfigured to fit in more hospitably with the street grid.
Likewise, there are huge swaths of "greenspace" that waste valuable real estate, often times for the sake of safety. I've been told that the government didn't want buildings across the street from the federal courthouse for safety reasons, but that is totally illogical since you can drive right by the courthouse anyway. After living in Washington, DC in the post-9-11 world, I watched as security barriers went up all around that city, despite many of the measures merely ruining public space as opposed to protecting anyone. For example, the federal courthouse in St. Louis has Jersey barriers up around the courthouse; they make the place look secure, but in reality would only stop a truck bomb from getting a grand total of another ten or so feet closer to the building. Certainly they make the area look bad, at minimal benefit to safety.
Also, work to make Walnut Street and actually appealing street to walk down; as can be seen below, the builders of City Hall clearly intended Walnut to be the grand vista upon which to approach City Hall. It is marred by a bridge from the jail to the courthouse. While I know it would cost large amounts of money, perhaps the bridge could be turned into a tunnel under the street.
Finally, embrace the juxtaposition between new and old; the area south of Market has lost much of its original character, but that does not mean that a neighborhood with its own character can't rise in its place.
Let's be honest, the whole area is dominated by courthouses, which in general are places people don't want to be unless they work inside. My experience is that many courthouse areas tend to take on a similar pallor as the courthouses around them. Likewise, government office buildings seem to have the same effect on creating drab neighborhoods. Consequently, the area should have a strong mix of all different types of businesses and housing to create a strong community in the Cupples Warehouse District.