About two years ago, I tried to do something similar to what you're proposing - retapping the crank. I'd accidentally cross-threaded the stupid thing.

I did a good job, too!

I managed over a thousand miles like that!

Then, about a quarter of the way into a century, my repair failed. I finished the century using a bolt threaded through my crank as a pedal. I'm sure you can imagine how comfortable that was. I didn't walk right for a week.

Just buy new cranks.