I have yet to spend ten minutes 'working' on my project trailer without wishing I was doing nearly the same thing on a four, seven or ten year old trailer.
Your passion can still be appreciated - it will just be in XX years by whomever is lucky enough to get your project trailer.
In any of the real estate parcels you've been involved with have you ever soundly cussed Joe Somewhen carpenter or electrician, home owner or renter for things they've done or left undone?
For every true Urban Legend of a saved Airstream renovation there are surely twentyfive that the inertia of unexpressed attention leads to a homely or even crippled trailer (look in my backyard, please.)
One pays a premium for prior diligent ownership - or a penalty for negligent. Let us study an old Airstream for a second. 1st and 2nd owners usually are not willing to leave their trailers unattended to become damaged by neglect. That is the biggest heartbreak of the old trailers I've been around.
Then comes the hand-me-down ownership complex where the capital investment is low enough that the trailer is not passed along when the owners attention drifts. Therein lies the second heartbreak, half-hearted or good intentioned repairs or modifications.
The factory design changes creep in incrementally - there is no engineering aspect "line in the sand" to flag for you. If you have a friend that needs a salary for six months full-time work while they reinvent every possible construction trade and tool known to twentieth century man then find a trailer that has sat unloved for X or XX years.
I don't know what year they started putting a rubber self-adhesive 'gasket' between the shell ribs and outer skin but that might be a good demarcation of where to start looking...
Again I apologize for being a real Boo-Hisser in your instance - I worked and got a early retirement from working on 40-ton Subway cars and it was a natural thing for me to want to see every nut, bolt and rivet in a 'affordable' (ghahahaaw) Airstream...
EDIT: Kevin245 posted the link to the checklist and a sober overview of Airstreams - remember to READ BETWEEN THE LINES (Thanks Kevin)