I would only be shopping for "clam shell" type campers if it will regularly be used throughout the Fall/Winter.
Northern lite and Bigfoot come to mind.
Taigaworks.com might be worth it to check out. I don't have one but their baselayers are quality and the bags at a glance look decent
I personally have EE 3/4 quilt rated to 0 and have brought it well below comfortably.
Sorry, cannot offer you a recommendation for cool pants with knee protection. Double kneed fallravens with thigh zips?
You consider a stand alone knee pad? I've run the arcteryx (combat knee cap) a few years ago in a blacktaill spot I had to crawl a bit. Yes, you sweat, but they can come off...
Misses has been running an osprey pack for 8 years now. It gets the job done, carries well, a lot of cute pockets for her organization. But I would go lighterweight next time as it's sub 4lbs.