We may not be the most useful resource. Some of us work on the gate, and might be able to tell you what there understanding of procedure is. I'm not sure that anyone here can comment on a policy level.
My gut instinct is that it would be like any other vehicle, towed or not--bring it in, don't drive it. I've certainly never heard of a fifth wheel having to detach from what it's towing. Although maybe I'm missing what you're saying. It can be difficult to contact the people who would know know, as many are on the playa and all are busy, busy, busy. And it may just end up depending on who's at the gate.
Lose your legs--Become a merit badge.
Remember, you're just a make-believe soldier in an artificial army.
"So many people have so little clue and there's only a finite amount of patience in the world!" --International Incident.