What IS unprecedented is having a C function bend over backwards to return an instance of collections.namedtuple().  

The only case I know of is with functools.lru_cache() and it was done there because we didn't really have a choice -- there was a pre-existing pure python API that already used collections.namedtuple().

ISTM the cross-version pickling issue is minor red herring.  We've cheerfully upgraded tuples to structseqs on a number of occasions and it hasn't been an issue.

Tim, would you please weigh in on this so we can put this to bed, either closing the request because we're too meek to make any change, 
upgrading to structseq to provide the requested functionality, or twisting our code in weird ways to have a C function become dependent on a pure python module.