What Steve is proposing is a rock guidewall about 6 ft in length, however high. If lots of hikers chipped in by bringing a rock to this area from either direction it would eventually get done. Breaking the job down into loose ideas:
1. Get the word out. Internet, flyer at trailhead, etc. Use marketing basics. "Move a rock campaign" of some sort.
2. Motivation. Honor fallen hikers. Help improve safety. Be a good person.
3. Knowledge. Basically all that's needed is a map location and GPS coords of where exactly is the guidewall and where does a hiker find a rock just before getting there (climbing and descending).
There may be better ways, but this just might work. Probably much quicker than getting official action on this project.