I have seen a patch that was brazed on a barrel in this type of location. Damascus barrel with a section of twist barrel used to repair a hole which was 10 x 20mm. It was an old repair which had lasted decades. So repairs can be done. I try to raise the dent and see if it cracks. Laser welding might be an option. Pressures that far out are pretty low.

Well first I would talk about price. That repair is risky and the selling price needs to be a lot lower to make me want to risk it. Others may be more open to the risk.