Thanks for looking into this westfw!
With your modified ArduinoISP sketch Burn Bootloader using Arduino AVR Boards 1.6.206's avrdude 6.3.0-arduino12 still fails, but with different output (see attached westfw_verbose_1.6.206.txt).
However, that sketch also causes Arduino AVR Boards 1.6.21's Burn Bootloader using avrdude 6.3.0-arduino9 to fail, with similar output to that of avrdude 6.3.0-arduino12 (see attached westfw_verbose_1.6.21.txt).
When I use the stock ArduinoISP sketch, my results remain the same as I reported in my issue report (success using avrdude 6.3.0-arduino9, failure using avrdude 6.3.0-arduino12, with ~same -v -v -v -v output).
westfw_verbose_1.6.21.txt (6.63 KB)
westfw_verbose_1.6.206.txt (7.08 KB)