Yeah, if it were possible to make the seal better, this could work really well...although it's basically just the same thing as adding a 2k turret to something except with 2 more barrels and bulkier. And maybe slightly quicker rotation.
I would say BBB from experience. It is fairly easy to mod and is very accurate. A NF would be cheaper and, if modded well, would go almost as far, but it's not as accurate.