[badrunner]

Something like this could work if a city is designed from the ground up to have two levels. A dark dingy lower level for cars, utilities and garage entrances and a bright upper landscaped level for pedestrians and storefronts. This upper level would actually be the architectural "floor" of a building with the main entrance. It's a concept I've thought about quite a bit.

But retrofitting existing buildings in this way is a bad idea. It just creates more dark corners in the bowels of the city and at the same time destroys the existing building facades and street level urban fabric.