Retrofitting a grease nipple without removal is a factory procedure. I live 350 miles away from my dealer and he has done a few of those but is adamant that he used HSS drill and tap.
The wall is 1/4" thick, I have gone over 2m deep after long time trying and using different drill bits. I should have gone past the hardened segment but nope.
So far HSS, carbide, cobalt, glass drill, and even a milling cutter.
I assume there will be no harm in trying the die drill you are suggesting.
I have even made a contraption, call it an upside down drill press.
