Devin,
You have come up with responses to all of the important issues in a breathable wall system, but of course, have also introduced a host of secondary questions as well. As an example: 5 1/2 years ago I built a 32' x 34' TF w/ 15' eave walls and a 8/12 pitch w/ Foard's R-30ish panels on the roof. I planned the walls as 12" thick woodchip clay, cypress clapboards on the exterior, a 3 coat clay based plaster on the interior. The frame is wrapped w/ 2x12 top and bottom plates w/ 2x3 studs, 2' o.c. Working with a handful of recommendations from Steve Chappell, we ran 1/2" x 1 1/2" poplar lath, 3" o.c., on the entirety of the inside of the stud work and window openings - jambs splayed 30 deg. or so; a must with thick wall construction, it gives you the most natural light and the opportunity for a deep windowsill/seat, and a chance to use all of those 3 - 4' slab and board cutoffs, thoughtful orientation of live-edge material can be used with great success as well.
Now with the interior totally lathed off, we hung sheets of clear plastic to protect the frame and floor from the inevitable overspray of goop(more poly than I usually care to use, especially in a throw away application, but it did its job perfectly and kept the planed and oiled frame very, very clean.

Next we hung 4-5' of lath on the exterior and, after having built a big culvert type mixer and two 4'x16' bins for media transport, we would drive the 12,000lb/50' tele-handler to the wall with a full load and two men on the platform. The platform was positioned to be level with the top of the last course of lath and the men would shovel/scoop/scrape the woodchip and clay into the cavity. A couple of tamps with a digging bar in the corners and then hang 4-5' more lath, move the machine, refill and repeat as necessary. 5 guys, 10 days, about 2,600 cu. ft or sq. ft - the wall is 12" thick.
Installed in May, blessed with a dry summer, began plastering in Sept. This system requires a good bit of moisture and consequently, adequate time and airflow to dry, hence the the 1 1/2" spacing on the lath - just enough to keep the material from falling out, but as much air as possible. The trick of putting some grass seed or been sprouts in the wall as a moisture meter is pretty cool too. They open after a week or two and die when the wall is dry enough to cover with either plaster or wood. The rain screen debate: I opted to place another piece of lath as furring strip in line w/ all of my studs to create a 1/2" airspace between the woodchip clay and the siding, now a true rainscreen. However, I neglected to plaster the exterior surface, or even wrap it w/ kraft paper - at this point in my life there was no way I was using Tyvek! The rainscreen is designed to draw air from below and ventilate at or near the underside of the roof surface, which is great, but when you don't have an air barrier between it and a porous material, you get air infiltration into the living space. The biggest challenge with woodchip and clay is this: it needs to breathe, but softly. The density of the material will assist in the air barrier function (like dense-pack (dry) cellulose), but can never be "sealed" in the modern sense with tape and glue and film and latex.
Quick Conclusions
-Don't install wet mix woodchip and clay against wood cladding(other than temp. plywood slipforms, ala Robert LaPorte)
-Seal woodchip and clay from exterior; design should reflect this, a tall VA farmhouse on a sloping site was not directly adaptive to this method of construction. The exterior was not plastered because it would've required thousands of dollars in scaffolding rental. When building natural/traditional be smart, think cottage style, stay single story or close to the ground when possible, utilize hip roofs to avoid big gable faces, etc. and always ask yourself if your design is commensurate with your method.
-I say either all cellulose or all woodchip clay, each with thoughtful detailing. I'll say more later as to why, but I've got to run.

Peace,
Jordan