I've never heard of a closet that wasn't tall enough to hang a full sleeping bag, unless you are measuring only from the bar to the floor. Raise the bar!
I am blessed with a 36 inch deep closet in my office/bedroom which allowed me to use 12 and 16 inch deep ventilated wire shelving. After designing what I wanted, I went to The Container Store and bought the pieces I needed to build in a completel modular ELFA closet unit. I also bought a few extra pieces - notably hanging bars - that allow the closet to be reconfigured to standard mode when we sell the house. Total cost less than $400.
The design worked so well that I put similar systems into each of the remaining walk-in closets in the house. That gave my wife a custom-designed closet for our bedroom, another designed for her sewing room and all its materials and the like, and a third for the guest bedroom - where our grown son still has tons of boxes stored.
Note the 24 inch SB - shelf basket - which has a raised front and back so nothing can roll out. I store my tents here. The thick black boxes at the ends of some shelves are really just bookends that clip into the up-rights. This keeps things from rolling off the side of a shelf. They also protect the down bags from things on the shelves beside them.
Note the short 12 inch bar on the right. I can hang two 6'6" down sleeping bags without touching the floor, and have space above the bar if I wanted them further off the ground. Since all the shelves are infinitely adjustable, the configuration can change as needed.
I did not include the optional cart unit, but it could be added to the existing structure easily, replacing the existing 19 inch wide 2nd section. Only the 5 vertical up-rights are permanently fixed in place.