I think I differ with your assessment of the NEC. Many of the rules and calculations laid down therein are actually for fire prevention, and/or end-user safety and convienience.
too many wires carrying current too close together is bad. wires poorly protected from nails, screws and water are bad. wired carrying too much current are bad. switches that operate in unexpected ways are annoying and dangerous. extension cords that are too long or overloaded are bad. Outlets that look grounded but aren't are dangerous to people and equipment. outlets that are too far apart are annoying. circuits that are wired with non-standard color codes can kill a DIYer or tradesman who is expecting things to comply with accepted and codified practice.
These are the things that the NEC seeks to prevent. even if there were no inspector, I'd wire to code just so I don't kill myself in 20 years when I've forgotten what I built in the first place and needed to repair or modify something.
Too, if you're not to code, and you have a fire or a shock, the claims adjustor is going to look at the report, smirk at you and tear up the check and your policy with great relish.
that said, a sufficiently large plastic gas line would probably be a good conduit. the UL, the fire marshal and the inspector will probably disagree on a 'standards' basis, but the basics are there; it's water tight and rated for burial, and even has a nice color for contrast with soil.
-Dan
