Update all of the Special Issues from the 1990s on hops, grains, yeast and include a new one on water. Most of those issues--while being very important--are almost 20 years old. I'm sure there are many things in those issues that can be updated and reflect more current grains, hops, etc.
It would be great to see a water issue. A lot more brewers are getting more and more involved with their water chemistry and there are a lot of great resources out there now that didn't exist a few years ago.
A refresh on those issues would be very, very helpful.