Good point, Prof, I forgot to mention my Thetford Campa Potti--and I thought I WAS answering the OP's question! To summarize: Don't get either a B or a TC, put a low shell on your truck and use it to serve a giant tent camp. I too thought about a small cargo trailer but couldn't find anything left to put in it after I'd loaded my roof bag, and there is the reduction in maneuverability to consider.
Also: Prof, your suggestion of the portable showers leads me to believe you've never tried them. I have, in several different configurations, and I can tell you that they all involve so much squirming around and contorting amongst the dust and pine needles that you invariably end up dirtier than before you started. The best method I found was an MSR Dromedary bag hand-held while you stand/crouch in the floorless vestibule. Still not as good as a sponge bath!
Lastly, Prof hits bone on the setup time. As I expanded the luxury/decadence of my campsite, what initially took an hour to set up now has expanded to almost three hours. To be fair, much of that time is spent with stuff like solar or sat that I'd have to do anyway with my TT. I never got my TT set up in less than an hour, and that includes pulling in to a highway Rest Stop for six hours of shuteye. Setting up a tent camp is more methodical and less painful than setting up a TT camp, but it does take more time.