Since you already have a good wool blanket in your kit, I would add something like an AMK Heatsheets blanket to it. I specifically say Heatsheets blanket instead of Heatsheets bivy because I feel that the blanket gives you much more versatility. While the bivy is good for sleeping in, the blanket could be used as a make-shift tarp, sun shade, wind break, rain catch, fire reflector, etc. much better than a bivy can.