I have a some code available for review here:

http://codereview.appspot.com/2340041/

I've actually gone down a farther path than I originally intended, but I do kind of like where this is heading.  It will allow me to install different Python builds of the same version without collision, at least when you use 'make altinstall'.  There are different versions even of python-config (with an added --abiflag option) so you can tell exactly what you're getting.

Note that 'make install' still adds all the symlinks so that you get a 'python3' and 'python3-config' as defaults.

Still broken are importing extensions.  E.g. if I do the following:

./configure --prefix=/tmp/python && make altinstall
./configure --prefix=/tmp/python --with-wide-unicode --with-pydebug && make altinstall
(cd some simple module with an extension)
/tmp/python/bin/python3.2dmu setup.py install
/tmp/python/bin/python3.2m
>>> import myextension

it tries to import the 3.2dmu version and fails.  I'm still investigating that, but in the meantime, please go to codereview and let me know what you think so far.