I've read your blog. You don't have to modify the Python core:

import copy
import types

def _deepcopy_method(x, memo):
    return type(x)(x.im_func, deepcopy(x.im_self, memo), x.im_class)
copy._deepcopy_dispatch[types.MethodType] = _deepcopy_method

I still wonder why you have to use deepcopy in your app.