John:
Your scenario does not fall under Recreational Vehicle, based on defs in Article 551
Also, keep in mind that the NEC is not a design tool.
Are you planning to run the rig from an onboard genset ? If so, you (or someone) has to determine the anticipated connected load of the equipment that you intend to use, then determine the gen size, and a panel size. If you plan on using the rig at the 'barn', then a xfr switch and a shore power inlet should be added.
Again, IMHO, follow basic NEC sections, and good workmanlike practices.
PS: I went thru similar situation with an Emergency Rig (Rescue/EMT) years back for a trauma ctr. It was a purchased rig that required a lot of modifications.
