Oddly, I agree with the 2 professional gunsmiths, CJO and Mark. Done properly there is nothing wrong with tigging the hook. My preference is to build a new pin, but as others have pointed out, it is not always cost effective. I try to match the best repair to the guns value. Most Birmingham boxlocks do not warrant a new pin, a Win 21 or a better grade sidelock, sure. It really comes down to what the customer wishes to spend in the end, after all, they are the one paying the bill.
Steve