...we do this for people at the co-op here, mostly as a service at cost.

You can no longer buy the heli-coil thingies and installation kit for pedal threading, but I think maybe you can get a spark plug one that is RH threaded in 9/16-20.

What you can buy is a kit with inserts that are stamped out of sheet metal, and a combination tool that reams the hole oversized a bit, then rethreads it to accept the inserts. These are available in both LH and RH threading. It's too pricey to buy just to do one crank, and the replacement inserts are about 5 or 6 bucks each.

I have no concerns that we are removing enough material to weaken the pedal eye, but I have some concerns about your description of the mode of damage and whether this is still an option.