Ed, ya got me thinking....
You know those tube-like "speedloaders" used for loading shotguns real fast? I wonder if something similar could be adapted for loading the "traditional" gate on the side of a lever action...? Ya think maybe? It would need to insert at a very shallow angle.... hmmmmmmmmmmmmmmm.
If we used a detachable mag, we might as well try to use a big one. I'm betting on the Brady Bill sunsetting, but just in case I wonder what the best guess for a magazine would be... Perhaps an FAL Mag with a block insert? I don't think an AR mag is wide/long enough for a 44 Spl/Mag/Supermag cartridge.
Yeah, I think if it was an 18" gun we'd have to go detachable mag, and if it were longer we'd go with the tube mag. I really like the idea of 870 furniture commonality. Sights are a whole 'nuther issue, though. Traditional barrel mounted rear sight, with a "flat top" built into the receiver, maybe?
Keep those ideas coming, all...