Why not just send it to Bobby Hoyt to see how safe it is to shoot as it currently is, and if it needs work, then decide what to do.
For myself, everytime I read one of these discussions where people recommend to take a weapon that has been HONESTLY reworked into something other than what it was when it came out of the manufacturers shop, and to return it to its original specifications; I can't help but think that they are recommending for someone to create an "honest fake". Because, even if the person today attempts to put distinguishing marks on it to prevent the weapon from being identified as a whole original, at some point in the future, an unscrupulous person will probably be tempted to sell it as a fake.
Left alone, it lives on honestly as what it truly is. A Civil War era percussion rifle that has been shortened & bored out to become a smoothbore. Whether this work was done in the 19th Century by a gunsmith for the local trade, or by some firm like Bannerman's in the 20th Century for the burgeoning, rebirth of muzzleloading here in the United States, to me makes little difference. It was honest work performed by honest tradesmen, for sale to people looking for a honest, low cost shotgun that could get the job done.
I think the gun has a simple beauty, similar to an English shotgun, and probably handles reasonably well.
Edit:
Not every surviving example of a firearm that was manufactured in whatever era, needs to be in pristine condition, nor looking exactly like an original. Honest wear & tear, coupled with the vagaries of whatever man & time has inflicted upon it, is what makes our sport so interesting.
Just like Joe Bonamassa wants all of his road guitars to have a story behind them, instead of being pristine examples that got purchased & stuck under someone's bed for 40-50 years; I think that guns like the one in the OP are far more interesting & important, than a high dollar collector's version of the same gun. ESPECIALLY, if there's a documented story behind it.