"nobody with Xcode 5 can build C extensions for python.org Python installations"

Andrew, can you elaborate on what problems you or others are seeing?  Xcode 5 should not be an issue for users of the current python.org Pythons. When building extension modules, if the compiler Python was built with is not available Distutils in the current 2.7.x, 3.3.x, and 3.4.x release will substitute clang.  This assumes they have the Command Line Tools installed, either through Xcode or the standalone CLT package and assumes that the user is not overriding defaults by setting environment variables like CC and LDSHARED which Distutils will honor without attempting to modify them.  This should all be independent of what compiler Python was built with.