I have been caught out a couple times on a forced bivy without a bag and it wasn't alot of fun. Both times were on summer climbing trips, nighttime temps in the low 40's. It was pretty impossible to stay warm; we had no pads, no belay jackets, just storm shells. Both nights we gave up and just started climbing again, in the dark, but it seemed safer than becoming hypothermic. I've also done this intentionally on a really light, LIGHT climbing trip. 2 foamies, 2 belay jackets, a bothy and a puppy pile. I lived, but I will never, NEVER plan on bivying without a bag again.
That being said, I think what you are proposing is incredibly dangerous. When on that light alpine climb, I was at the peak of fitness, with nearly 20 years of outdoor experience under my belt, and I was accompanied by two equally fit, experienced partners. We knew EXACTLY what we were doing and were well aware of the potential consequences. More weight would have made the climb nearly impossible, so we made an educated, calculated judgement. Not a guess, and not hoping for the best. And it still turned out far worse than we thought it would.
Try it in your yard if you want; set an alarm so you definitely wake up and can check your status. After you nearly freeze, forget about trying it ever again. A quilt can weigh as little as 11 oz. If this is too much weight, stick to day hiking, in warm weather. I hate doing body recoveries in the snow.