Toughbooks are tough, but not impervious.
I have seen what happens to Toughbooks in the hands of sailors on an aircraft carrier, and I see what the aircraft mechanics at the airline I work for now do to the ones we have.
It isn't pretty. With that said, they still function, which can't be said for the average consumer laptop if employed under similar circumstances.
I agree: a Toughbook, though expensive, would suit your application. Just make sure your guys know and understand that these machines can and do get broken, and if it were me, I'd be ready to dock the pay of the first guy who put even the tiniest scratch on it.