I also miss being able to pickle unbound methods on Python 3. I don't think there's an interest in pickling the actual code objects. In my opinion, unbound methods should be pickled exactly like all the other Python definitions, such as bound methods, top-level functions, and classes: They should be pickled by name.

IIUC, the challenge is how to figure out on which class an unbound method is defined. I'm using the term "unbound method" colloquially, I know it's implemented as a function. So perhaps Python needs to be changed to give unbound methods some attribute that will tell on which class they're defined?