I doubt he could do mine, even though there are no paperwork hurdles to jump over. A couple of my roles are a learnt skill which takes a couple of years to become proficient and there is an awful lot of appreciation of what other departments do that influence my job. Other roles are just knowledge and experience based, he'd be a fish out of water. I reckon I could jump into the cab of an tanker and drive it, almost ceratinly not very well but at least I'd get it to move.
It is walking on very thin ice when telling strangers you can do their job. ISTR you can do an intensive crash course and get your HGV1 in not much over a week. I should imagine there are similar course(s) available for the safety certification. Anyone would then be as "qualified" as him to do his job. And at 40k a year it's tempting...