Hello all!  Short-time lurker....

After reading everything I could from Building Science Corp. I am left with one question: 

I'm building a tiny house on a trailer (150 square feet - a la "Tumbleweed"), complete with a kitchen, a bathroom (marine "composting" toilet and shower), a loft with shed dormers and a tiny marine wood stove located in Vermont.  I want to use real T&G wood paneling (considering either hemlock beadboard @ ~1/4" thick or 1/2" V-joint pine or white cedar) to cover the walls and the cathedral ceiling.  If hemlock or pine, I plan to apply a linseed oil whitewash. 

Everything out there discussing interior vapor barrier/moisture control assumes sheetrock walls/ceilings with one coat of latex paint. 

So, I am trying to figure out (1) if I need to worry about and/or (2) how to prevent interior water vapor from entering the wall assembly and condensing on the sheathing.  I plan to use either fiberglass or wet-blown cellulose insulation in each reclaimed native full 2X4 wall cavity and each nominal 2X6 rafter cavity.  I am able to wrap the exterior with at least 1/2" up to 1" rigid insulation to mitigate heat loss via the studs/rafters and to deal with dewpoint/condensation issues on the cold side of the wall and roof assemblies.  The rest of the wall from the studs out will be plywood sheathing, Tyvek, and a rainscreen exterior wall using pine furring strips and heart redwood clapboard siding.  The rest of the roof out from the rafters will be plywood sheathing, 1" XPS, Tyvek, horizontal furring strips & standing seam metal roofing (galvulume).  The house will be tight; I will follow tight-building techniques. 

So, foiled polyiso & taped seams on the exterior (i.e. "Warm-Wall") scares me since it will not allow any drying to the outside.  XPS would be better; it seems to allow some drying to the exterior.  Is drying the outside even necessary in such a small dwelling?  I worry that interior moisture issues will be compounded in such a small enclosure, even if I take steps to mechanically vent it (the toilet vents to the outside via a small solar fan that runs 24hrs a day and I will install a through-the-wall passive adjustable vent near the woodstove for makeup air).  Conventional houses can absorb so much more water safely produced on the interior than I suspect a tiny house can.

But what to do, if anything, re: vapor control under the interior wood paneling?  And what if I don't wrap the exterior walls with XPS (or polyiso)?  And what if I do wrap the place in rigid, but one inch material (which is as thick as I can go because of my design and maximum DOT width restrictions) is not thick enough for my northern climate to prevent condensation?  I have not yet run a dewpoint calculation.

I thank anyone and everyone who takes the time to reply.  Your help is most appreciated!  :)