I’m surprised this didn’t generate more discussion. I have often wished for the ability to sample more than four points also. If you do a Google search on "digital zone system" you will see that many people have talked about the concept, but there is little in the way of usable tools. One Photoshop plug-in is Ozone <
http://www.digitalfilmtools.com/html/ozone.html>
which would seem to have some potential. It divides the image into 10 zones. Unfortunately, I have found it to be nearly unusable since there is no way to get a readout of RGB values while you are making the adjustments in the Ozone window. Not only does it not provide its own readouts, but it disables the Photoshop Info palette readouts as well. So, while the plug-in provides a number of sliders for adjustment of each of the 10 zones, you must judge the result visually. Seems like there is plenty of room for someone to do it better.