Okay. Attached is a patch that doesn't import pkg_resources and doesn't reload anything. I haven't yet tested it -- I am submitting it only to inform the discussion and get any early feedback from you on whether the very idea is sound.
Okay, I tested this patch on Mac OS X and it worked. First I installed setuptools v0.6c3, then I tried to execute allmydata.org 's "setup.py install". I got the error message saying that it couldn't install a newer version of setuptools (v0.6c7) when an older version was already loaded. Then I applied my patch to ez_setup.py and tried again. This time it installed v0.6c7.