[gumby]

I was a big fan of this but it's harder than it sounds. After all, we all know of some great commercial conversions from prior generations (most of the southern part of Manhattan, for example).

Unfortunately the big modern office towers often aren't constructed in a way that supports apartment conversion. There are lots of offices in those buildings with no windows, and all the service(i.e bathrooms) are in the core. Retail space is often worse in this regard, especially in malls. The renovation costs often end up higher than demolishing and building anew.

I still think you're on the right track though, it's just that the obvious fix is harder than it looks. But I do believe cities are in for a great renaissance of mixed-use buildings.

[plasticchris]

Maybe apartments are the wrong paradigm - this sounds perfect for creating something like a dormitory with rooms on the perimeter and shared bathrooms.