Check out Borah Bivy. I've used an oversized bivy sack for a few years now & love it for what it is -- bug protection and emergency weather protection. Longest I've stayed is 3 nights at a time so not real long-term. I got the smaller tarp to go with it and, in retrospect, I wish I would have gotten the larger one. It's extremely light and small -- probably 10-12 oz plus whatever stakes & cord you bring. Wasn't very expensive, as I recall. Also made by hand here in America by a small business owner (as in the whole company is just one guy sewing these things) -- things I feel good about supporting.
I've started to relegate it to more of the ultra-light packing category when I spend all day covering miles, not sitting in camp or awake enough at the end of the day to read at night, sip on some tea, etc. So it doesn't get much use for hunting. I'm way slower & more relaxed for most hunting so I like a more comfy camp. But for days of long, hard miles, my Borah Bivy & tarp is in my pack.
If you're looking for a compromise between a light-weight tent and a ultra-light bivy, you can always pair a floorless tipi (trekking pole setup) with a bivy sack or even just some netting for bugs. tuck the netting under your sleeping pad & you're good for almost anything nature can throw at you in the warmer months.