I would like to have a volume control (similar to the one in the amp and cab section) in the EQ section of the stack.
Why? Well, I find that the difference in volume once you tweak the EQ in the stack to your liking significantly influences the overall volume. Especially in the mid range. Now, we all know that higher volume is (psychoacoustically) perceived as better (sound) - which makes it hard to evaluate your EQ tweaks. Of course, I could go the the cab or amp section and adjust the compensate for the volume drop or boost there. But that's not an ideal workflow. The volume knob on the KPA is something that I like to keep in the middle so that there's is enough headroom for when you set up your sounds for a performance.
I seem to remember that the volume control in the amp section was at some point added - it wasn't there from the beginning. Now, I wonder, why it was added in the amp section, because tweaks there have a lot less influence on the overall volume. The EQ in the stack would be a very convenient feature and maybe encourage users to make use of the EQ in the stack more.