What is the cost of rethreading the existing crank for a pedal, vs buying a replacement crankset? Since you're doing the work, I assume the cost of the repair is essentially zero. I'd go ahead and attempt the repair, and if it works, great, you've avoided the cost of a crankset. If it fails, not much lost.

I don't think the failure mode would be catastrophic, surely the pedal would bend noticeably before flying out completely.

I had to have a stripped alu crank repaired by a shop once, they used helicoil. It cost me I think $40. I have had no issues with it since (thousands of miles of riding). I'm 230ish, but I also always use 20mm pedal extenders, which significantly increase the leverage on the pedal eye.