I have never had a metal barrier on any of the carpet vans I run. (I am an employee) however, at the last company I worked for, I bitched like hell until they let me run the box truck, for the reason of safety and AC...
My argument went something like this: You dip$hit brother and his friend don't even wear seatbelts, why do they need the safer rig? Have you seen what a mess it is? That's because they are unwilling to climb up in there to get things, so they throw everything in the back, why don't you give them the cargo van? It would be easier for them to keep it clean...
It worked... until I tore the mirror of the box truck, then I was back to the cargo van...