Steve:
I wish you well... having a plan and then waiting til it's the right time in your life is a special thing. I'm building a small houseboat right now on top of an old 24' pontoon boat-- an idea that swirled round my brain for a decade. I plan to launch it on the lake next spring.
Sounds like timberframing is w/in your grasp, not only because of your background, but for a strong fortitude to see it through.
Sawn timber is a better choice for sure. And Purlins do have that look.
If you've been lingering around here for a bit, the question I have for you now is, will you be using continuous top plates or a "Connected Girt" (CG) design?
A CG frame is well suited to a purlin roof. It may also have some raising advantages if you'll be short on manpower, etc.
