But I seem to recall that rifled shotguns are a thing that exist, though they are most effective when used with slug... Which can also be had rifled. I'm not sure how hard on the shooter this would really be, 12ga can be hip-shot, after all, and this beast is going to be HEAVY, so as long as there is somewhere to put your off hand, all you'd have to do is ride the recoil. Firing something like skeet loads, your arms would get tired holding the gun up long before you'd have any real worries about recoil induced injuries, imho.
Building it would be entirely possible, but the entire frame, at minimum, would be custom. You can (probably) use an off the shelf barrel, with some modifications, but at the end of the day, I could see it being easier to custom make everything else, rather than trying to adapt an existing firing mechanism.
TL;DR, you can build it, and perhaps even shoot it, but it would be really expensive, and require a lot of machine shop time.