The footprint may work, it depends on the material and its coating. My concern is that making a pack properly takes time and effort which may be more-or-less wasted if you use the wrong materials.

With that said, in the past, I basted together a pack from some hideous, bargain shelf, 50 cents per yard, floral print. It took some time and a lot of fussing and the resulting pack looked really weird. But, I wound up with a pattern that has evolved over the years into a pretty good, 12 oz, 42 liter, lightweight pack.

My main issue with the G-4 pack is that it is too big for its suspension system and I don't like the outside pad pocket. YMMV.