Joe, sounds like you have thought this out well, but here's my 2 cents.. I have not hiked that Hut to Hut traverse, but done similar hikes here. I always carry 1 emergency shelter and at least 1 summer bag for two hikers even if I plan to stay in a lodge which provides a bag. I carry a 9oz goretex bivy sack and a 1 lb down bag, both wide/long models which can accommodate two people in an emergency. Reason being I might get lost off trail, be stuck between huts due to an injury, or have to bail out on an escape route (non-trail route back to civilization) and so might have to bivouac.
As for clothing, I recommend a system of 5 thin layers, just vary the thicknesses based on record lows. L/S base, windshirt, breathable(not windblocker) fleece 100 for on the go insulation, maybe a high-loft jacket for times when I'm stationary, and a WP/B rain jacket. If lows reach records I can double the fleece under the jacket.
Maybe that's overkill for the altitudes and temps you expect in Summer? I thought it would be for Japan but last weekend I was at 3200 meters and the wind was whipping; with the windchill it was about -9F and I was wishing I brought my Thermawrap in addition to my fleece!