gpy-upgrade-impl --fix should modify the latest non-live ebuild, in addition to the latest ebuild. This would assist in getting the latest ~arch ebuilds tested with new python versions.
Since gpyutils has already some code for handling keywords (for gpy-counts), I guess this would be relatively simple to implement. I'll try to take a look at it in the EU evening.
Fixed now. https://bitbucket.org/mgorny/gpyutils/commits/80503aa8 The bad news is that the mangling code seems to be a bit broken but that shouldn't affect 3.3 -> 3.4