If few people use file names not in their respective CP_ACP as you say,
why did Microsoft bother to make Windows XP a unicode OS?
It does not make any sense.
The existence of such bugs is the source of the problem itself.
It is because of this situation that people in non-English speaking
countries prefer to install English Windows XP. After all why should
they get all messed up with incompatible software?
And from my experience a considerable percent of these
stay-on-the-safe-side users have their CP_ACP pages setup incorrectly.
My software installs per-user Python modules in a sub-folder of the
User's Application-Data folder. The software itself resides under
Program-Files. The User's Application-Data folder will contain unicode
characters if the User's account name contains unicode characters.
You can argue that the design is good or wrong or can be altered to work
around the problem, but the fact remains:
Python is Broken.