Getting the advice of the staff at the pointy end is a good recommendation. But. During the late unlamented Advanced Automation Program I watched some of that happen. A group of controllers met with the contractor and provided human factors input to color of screens, trackball feel, etc. Fine. A couple months later the controller human factors input was provided again, by a slightly different group of controllers and guess what...it was for different colors, different trackball etc. The contractor loved it all the way to the bank.
What was interesting seeing this was that the controllers were playing engineer. And when I watched the design meetings between the governemnt and contractor engineers the engineers played controller. This was not the first or last time I had seen it but it seems to be a common phenomenon (sp?). Just think what could happen if a few controllers and engineers got together and the controllers were controllers and the engineers were engineers? Believe that is what happens on some successful programs maybe?