[Killo1]

Marshall.
As you know, salt water is brutal on metal. None the less, I think you should start working for Airstream and help them with small, but significant improvements as you had mentioned. I love the way you think.
If you feel brave may I make a few suggestions?
Pull the whole frame and have it professionally powder coated. That should hold up a long time in your environment. If the powder coating is prepped correctly the powder coat is great barrier. You also might try Emron, but you would need someone to beed blast before you paint with the Emron. Emron is a great two part paint/epoxy. Used in aviation alot as a barrier for magnesium and the elements.

Secondly, use stainless tubing for your propane. It would take a little more work, might need to rent a pipe threader and bender but it would be bullet proof.
Keep up the good work. Try to throw in some pictures if you get a minute. Would like to see your work.