I think you'll find that the "whoopee cushion" bags are no different from the ones you can (optionally) draw down with your vacuum cleaner. The larger of those bags (e.g. Coleman) has a one-way valve that will fit your vac. hose. However, they're no more nor less stable than just rolling it down yourself. No difference, IMHO.

As to the food saver type vacuum packer: I've never seen one you could use for anything as large as a blanket. The largest bag I've found is 12" wide (length is up to you.. on the roll). The largest sealing area on the unit is 12" wide. Unless you have access to some commercial grade vacuum packer, I think you're stuck.