I'm a die-hard bivy user. in my "quest" for perfect gear, i have acquired several, ...er...some,...er..., the truth - many!!
i like the simplicity of a bivy - especially when "pitching" in a torrential downpour. though a skilled tarp camper (NOT me) has methods for staying dry while pitching.
noticed several pts on your list at which wt could be shed - i'll mention just one.
first, let me say. you're doing the right thing - going lighter. i started traversing this exact same route over a yr ago. my motivation was age/physical condition. yeah, 80lbs was doable (more like bearable) in the military. 50-55 when i was still in my early-mid 40's - though i was definitely feeling the wt, esp.going up&down hills. it took an accident (a fall from only 8 feet), when in my late 40's, that laid me up for 4yrs to force me to go L/UL. it should have been common sense, but i guess i had a chip on my shoulder as to how much this aging body could still carry (a stupid, macho carry over fr/training for power lifting competition as a much younger man). i'm having more fun on the trail now with 15-20 lbs total pack wt, than when i was a kid & far stronger young man carrying 3x the wt. my base pack wt is 7.5lbs for above freezing temps.
How about lighting up the bivy a bit? since you like Bibler, what about this? while i've never owned a Tripod, i have studied it closely & learned as much as i could about it. chose the Bibler Bipod Bivy instead. quicker, easier to setup - this is great when pitching it in the rain. still has enough head room & interior space. save b/t 10oz & 14oz in wt over the Tripod (depending upon whose wts you read for each bivy). Have you thought about the Bipod? ...or, even a poleless bivy having just a wire hoop (or no hoop at all)? these are far lighter. as long as you're not claustrophobic, they work well - IMHO. i also like the Integral Designs Unishelters (both eVENT & TegralTex - similar to Bibler's ToddTex) & Salathe (TegralTex). You might check them out. ID told me in a phone conversation a few months ago (not with Evan Jones - don't know who it was on the other end of the line) that they may make an eVENT Salathe in '06 - this isn't definite; they were only thinking about it at the time.
On a diff note, what I'm carefully considering at this time is the SixMoonDesigns Lunar Solo 'e' - a full blown floored single-wall tarptent that weighs 24-27oz depending upon the wt of the floor chosen. Lighter than any pre-bent, sectioned pole bivy. requires one trekking pole (or some type of pole/branch) to pitch. If you check it out, or try/buy it & have any opinions, maybe you could share them. I for one would appreciate it.
ok. i lied. a second place to shed some wt. the "footprint" for the Bibler. try GossamerGear's Polycryo 1.3oz ground cloth. very inexpensive. when i feel that i need to use a groundcloth, i use them. work fine.
thanks for taking the time to read my comments. Godspeed and good luck on your journey towards the light.