I've doen something similar to what you describe. I'v added a full bottom to the quilt using a single layer of uncoated nylon. I've done this for both a single and a double quilt.
This really cuts down on drafts and gives me a lot of range, temperature wise. I can, for example, roll the quilt a bit so part of me is under single layer nylon and part of me is under down. If I want to tighten things up I can bunch up the single layer nylon under me using my hands or feet.
With the current availability of lightweight nylon a bottom like I'm describing could be added to any single person quilt for something like an ounce of added weight. Well worth it in my opinion.