There was a previous try to use a file encoding different than the locale encoding and it introduces too many issues:
https://mail.python.org/pipermail/python-dev/2010-October/104509.html
"Inconsistencies if locale and filesystem encodings are different"

Python uses the fact that the filesystem encoding is the locale encoding in various places. For example, Python uses the C codec (mbstowcs) to decode byte string from the filesystem encoding before Python codecs can be used. For example, the ISO 8859-15 codec is implemented in Python and so you need something during Python startup until the import machinery is ready and the codec is loaded (using ascii encoding is not correct).

The C locale may use a different encoding. For example on AIX, the ISO 8859-1 encoding is used. On FreeBSD and Solaris, the ISO 8859-1 encoding is announced but the ASCII encoding is used in practice. Python forces the ascii encoding on FreeBSD to avoid other issues.

I worked hard to have Python 3 working out of the box on all platform. In my opinion, going against the locale encoding in some cases (the C locale) would introduce more issues than it solves.