As you are no doubt now aware, the crank threads on
the spindle socket present some unique problems in
the rethreading process. It's a pretty shallow, flat
bottomed hole, so you cannot just take a standard
tapered tap and run the sucker through.

I've never attempted this myself, so can offer no guidance
or suggestions, other than I really do not think it would
be a very good spot to try a helicoil either.

The jacobs chuck thingies seem to work reasonably well
once you get the hang of it, and as has been mentioned,
you really do not have to pull the cranks all that often
if they've been serviced and installed correctly.