In fact, PEP 3003 says explicitly, under "Case-by-Case Exemptions":

"""
New methods on built-ins

    The case for adding a method to a built-in object can be made.
"""

So I'm changing the version back to 3.2.  Having said that, I'm still -0 on this change.  I can see some (small) value for bases 36 and 62 in particular, but little use for the other bases.

Incidentally, Yuvgoog Greenle did bring this up on the python-ideas list (thank you!).  The thread starts here:

http://mail.python.org/pipermail/python-ideas/2009-August/005611.html

The thread was rather inconclusive:  it got bogged down in discussions over whether bases 37+ should be allowed, whether there should be options to specify the digit-set used, and the like.