Thank you for the input Stefan. I was actually glancing at _decimal as an example of implementing pickling and inter-compatibility between the C and Py versions of pickles.
You've chosen compatibility by having the same class name and __reduce__ returning the exact same tuple for both implementation. This is a pretty good idea.
Unfortunately, in the case of Element it's more difficult, because the existing Py implementation does not have __reduce__, so pickle does its thing by looking at __dict__. Changing the Py version to have a __reduce__ seems risky as it may break compatibility between the different Py versions of Element (say, from 3.2) and this is bad.