I think the answer would be yes (it would fire reliably). Many over/under firearms were made in this manner. The less complicated version has an extension welded to the nose of the hammer on the left gunlock and a standard drum and nipple on the lower barrel. The cheaper method is more direct, but not quite as pretty. My Beretta over/under 12 ga. shotgun works reliably now that the holes are all aligned properly.
James Levy