Please remember that a potential new pickling feature is the least import part of the design of methodcaller, itemgetter, and attrgetter.  Pickle support should be driven by the design rather become a predominant consideration.

One other note:  the OP's original concern has very little to do with these particular objects.  Instead, it is the picking and unpickling tools themselves that tend to have crummy error messages when presented with objects that weren't specially designed with pickle support.