I see no problem with a shim if done properly. I think there is a negative connotation around shim because people use all sorts of things i.e.. paper, aluminum cans, and perhaps try to sell a gun with such a crude repair.

If you get a steel shim, solder it in and check the bearing surfaces of the barrels to receiver I think it is a permanent fix no better or worse than replacing a pin or welding up the hook.

Nothing is foolproof to a sufficiently talented fool.