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.
Today's hiker has very little basic knowledge and wants even less...unfortunately. Most cannot find the north side of Sunset Blvd. from the southside. When asked how to they would get out of an area if their ascending route was block by fire 1 in 1,000 might know...I know this because I ask. Good luck getting many who think it just fine to leave egg shells, banana peels, apple cores and WAG bags behind to carry a rock.
If you do not get official approval, this structure will get torn down. This is how things work.
Lastly, for everyone who wants this wall, there are a like amount who do not. Last winter, the Angeles National Forest was inundated by calls for elected officials after they "soft" closed the forest in the Mt. Baldy area after multiple deaths in February. This after they had been called by the the citizenry to close it.