Oh, and, as to whether Argument Clinic would solve this problem, the answer is "not yet".  Right now Argument Clinic literally generates calls to PyArg_ParseTupleAndKeywords.  (In special cases it switches to PyArg_ParseTuple.)

I'm more interested in Argument Clinic from the API perspective; I wanted to make a better way of specifying arguments to functions so we got all the metadata we needed without having to endlessly repeat ourselves.  Truthfully I was hoping someone else would pick up the gauntlet once it was checked in and make a new argument processing API / hack up the Argument Clinic output to make it faster.