This was done for a TA crank once, but at a time when crank pullers were in comparison to today's cost, cheap.
Sacrafice an extractor and turn it into a tap, need a grinding wheel and one who has worked at a machine shop would be best, cut three scallops away from the threading, clean up the "leading edge" and go treat it as a tap. Locating a bottom tap in the TA or Stronglight spec. would be a non starter I think, I doubt even a Helicoil will be avail. in a practical size for this and the Helicoil system usually needs more depth to work with, at least all the units I have used.
A case where a replacement crank arm set probably is most cost effective.
The previous "knock out" methods will work, done them when a customer botched a home mechanic attempt, but we never reinstalled a suspect arm.
John Jorgensen
At work in Torrance Ca USA