DIY Canvas Bag

[jlw0142]

I have been thinking about this for a few days and would like some opinions on whether this is a good idea or a dumb one. I have been considering getting a sewing machine for DIY projects. I would get several yards of poly cotton canvas and midweight flannel and sew them together, stuffing the inside and creating a sort of fluffy sleeping bag, but pretty large so i can fit my sleeping bag inside. I would sew a 3 inch foam mattress into the bottom side and would also stitch in a pillow. Similar to a canvas cutter, but no poles. Any additional ideas or recommendations would be great. Or feel free to tell me that you don't think this will work. It would mainly be for truck camping and backcountry situations where weight/bulk is not an issue. Thanks.