I agree we could have done it a lot differently and safely, I especially like the last point you mentioned that is what would have been the correct way to do it

I agree we could have done it a lot differently and safely, I especially like the last point you mentioned that is what would have been the correct way to do it. But this happened as described, a local only script that generated a list of columns to modify then a migration to execute the alter queries for all of them.