I realized in his thread discussing Gallery Models, Thriver mentioned that the walls in his museum are reinforced with plywood that is set behind the drywall and runs from the four foot, eight feet up the wall to the twelve foot mark.
I have heard of the same set-up being employed at other museums and it was what was specified at the the Getty when I worked there as well.

Thriver expressed some concerns about installing below the four foot mark and describes a method to "bridge the gap".

I agree with his accessment.
In addition as hard as it might be for folks in museums with some kinds of collections to envision I have personally had to install hanging hardware above the twelve foot mark on several occasions. Obviously if you are installing something that high there is a fairly high probability that it is large (and quite possibly heavy).

As well I have had to install "L-Shaped" brackets or ledges to support the bottoms of artwork on several occasions. There again they tended to be large and heavy objects and as such the bottoms were below the four foot line. While at least in this scenario the placement of the anchor doen't have to correspond to the hanging hardware of the piece but instead (depending on the length of your bracket) can potentially utilize one or more studs.
Still though with the prominent current use of metal studs (which to me represent no real sense of security) it would be more desirable to have actual backing in the walls at those heights as well.

I would recommend any institution doing new construction that they consider instead of ply backing being installed from 4' to 12' that another sheet be added to run from something like 2' to 14".
Before folks start balking, remember that if you are reinforcing the walls at all this will represent a relatively small addition to construction costs.
Once you put in any plywood, anywhere in a wall the real added expense comes in the form of the labor required to "block out" the entire wall so that the drywall is even.
The additional sheet of plywood at the time of this writing would come to $3.25 a running foot of gallery wall space (for 3/4" CDX) and that is if it is purchased retail at a local mom and pop lumber yard.
The added safety and efficiency gained spread over the course of many years would seem to justify making this adjustment to the standard.
Just some thoughts