I have been thinking about this for weeks now. I even slept using my Refuge-X as a blanket to see what the fabric is like for this use. I figure I can make a quilt, much along the lines of this one
The differences would be
a) silk baffles
b) a velcroed closure along the bottom baffle that is covered with silk to allow the air to escape when packing
c) the baffles will be attached to the cuban with cuban tape to make it almost completely waterproof (ie no seams exept the edges and fabric joins).
I am also contemplating an openeing so it can be worn as a serape...not sure about this, and tie-outs along the edges so it could potentially even be pitched as a shelter.
Dimensions, around 66" at the shoulder, 52" at the foot, 74" long, baffles at 6" intervals, 2.5" high, fill weight ~10oz. I'll go with the gossamer light 0.33oz per yard fabric, with a guesstimate of ~7 oz for the cuben, 3oz for the tape, 1oz for the baffles, for a total of 21oz. I would conservatively guess it would keep me warm down to almost 0F when used with a skaha hoody.
For you hard-core ULers, this could be scaled down to Arc alpinist dimensions for a truly UL waterproof VBL sleeping experience.
Yeah, it's really wide, but that's how I like it, so it can be virtually turned into a "bag", and can also be used as a two person quilt.
Waterproof, light, VBL, shelter, insulated clothing...what more could I want in a quilt? Well the down sides are gonna be cost (yikes), crinkly sound (but I'm OK with that as I don't move much in my sleep), non-breathable could get sticky in warmer weather, durability.