I dunno, cab-off is only half the story. You've gotta move axles, suspension, steering, motor, fuel tank, all harnii that run down the frame along with emissions and evap lines and other things I'm forgettingLook at all the cab-off work that needs to be done on HD pickup trucks these days. Ford techs must be pretty good at this type of involved work. Nissan techs? Who knows.
I agree it's not rocket science but a careless tech will have the vehicle wind up with Eric O as he chases a single wire that chafed through because a harness was carelessly anchored

I still wanna see the alleged failure that would prompt Nissan to say, "One new frame comin' right up!"