One way I can see to have the vise hanging out away from the saddle is when you would mount the vise on one end and rotary table on the other and then work back and forth on them. Maybe a gun barrel clamped in the vise and moved over so you can drill the gas port. I think you should consider what you want to do with the vise. My 5" is great on a similar size table. It opens just shy of 6" so it is a good capacity and even more if the jaws are moved outboard.
Dave
Dave