My PBC is very similar to a smaller UDS. That's the reason I went with it. I debated for a long time on building a UDS, but I just didn't have the ability at that time. The one thing I hate about a UDS, and my PBC, is that there is one chamber that holds the food and the fuel. If you're on a long smoke you better hope you have enough fuel in from the get go, you can't add any after the smoke starts.
I'd go one of two ways. Small fire box mounted to the side at the bottom of a drum. Then I would have one, or two, door cut in the drum. My worry there would be the grates would have to be permanently mounted in the drum. Being the drum is round, I just don't see a feasible way of mounting them otherwise. Or go complete build using the same basic design as the one I just went over, but building a square 'drum' for the food. Then I could use a few racks in the top 2/3 of the square drum, have a door or two, and allow them to slide out. That would also allow me to put a fluid bowl in the bottom of the square drum to keep moisture in the chamber. All while allowing all of the individual variables to be tended to individually without opening everything up.