Anything is mendable.
It needs the whole thing bolting to a solid steel face before setting about it, with the silencer end in a fixed jig thingummy. Then, cut out the bad bit, replace it with a good bit of steel and start over making it up.
The problem is the time it takes is not worth the price anyone would be willing to pay.
If the guy who knackered mine had bothered to bolt the flanges to a steel bar before he started, what he produced would have been well worth what he charged me, which was a paltry £60. But he didn't and his welding pulled the four headers around and it looked like a Medusa after he had finished with it.
If only I could weld...