You need to concider how sleeping bags are made. You can not just take out the insulation. It is sewn in in many places. You need to rip out seams, alot of seams. As previously mentions, you could re-use the materials, but you would be saving only 40-50 dolars and you would be degrading the materials. The zipper might be worth salvaging as they are 10 dollars.
Possible... kinda. Worth it... not realy.
I had superhuman powers, but my therapist took them away.