Well, Russ, I have actually held one of the real ones* and it is a bear to handle. It is muzzle-heavy as all Hell, as you might well imagine and it was not what you'd call an effective cut and thrust sword, either. On the whole, pretty much a loss, IMO. And I would expect that anny such weapon would be the same. Bayonets make a rifle awkward to shoot and so would they do to a pistol, IMO, including the folding spike bayonets that I have seen on some old muzzle-loaders. I should think that the better option would be the road obviously taken by the old "Hoss Pistols" used by cavalry and dragoons in the muzzle-loading days; make them heavy enough for them to be turned around and used as a club. Why do you think that the old front-stuffer pistols had big balls on the butt? Ugly as sin, but effective as a warclub.
* At an NRA National Convention in Washington, DC(?!?) in Spring of 1960. An exhibitor had one that he let some folks handle.