I'd think it's good to be aware, but I think there would be so much more to barrel making and putting it together to become part of a rifle, than just one small part of the whole picture. It's not related the proposed rifle, but there's a well documented single shot rifle that was featured in Precision Shooting magazine and shown on line. It has a cut rifled gain twist barrel made out of rebar. The point being, it was a stunt, but put together with a high level of expertise and seems to have turned out to be quite a shooter. I personally have no plans to commission a custom muzzle loading barrel, but to a large extent I think confidence would come more from experience and reputation. On the surface, 4140 is a no brainer, but there are probably more than a few of those that have blown or not shot very well.
good point; i know of no Colerain barrels rupturing
