This is one of those ideas that is not just a "cool idea", or something that I just have a random kink or obsession about. This project would be genuinely useful to me. Enough that I have seen other designers do exactly the same project, design organizations, such as AIGA, and others.
The problem essentially is that most people really don't understand what graphic design, or design in general is, or what its value is. It also happens to be these very people who would benefit most from design.
What I need, as a designer, is a booklet, a manual, or something that is easy to read, well designed, and not only explains why design is a valuable thing, but demonstrates it in a clear and obvious way.
It perhaps shouldn't go into too much detail about how to design something, but through popular examples.
For instance, the most obvious example is the iPod. Now, hindsight is 20/20 of course, but according to the logic of those who don't understand design, the iPod should have been a failure. The iPod wasn't the first mp3 player. It wasn't even the first hard drive based mp3 player. It was more expensive than other music players when it was first released, and still is. In terms of hardware, it doesn't have as much capacity as other players, and didn't when it first came out. It doesn't play as many formats as some. The iPod was even the last digital player to play videos. About the only obvious advantage it's had is that it's slightly smaller than the others. If you look at it in these terms, it's a complete mystery why the iPod has been such a success.
There are other examples too. The branding for chipotle, the architecture of their restaurants. Starbucks, flckr, and others. With no obvious advantage over competitors in a purely statistical standpoint, it's clearly the superior design which gives these companies the win.
There are smaller scale examples too. The clarity of communication in a sparse design which makes good use of negative space, vs. a crowded design which sees empty space as wasted space. The direct financial benefit that comes from designing an ecommerce site to channel viewers into becoming buyers- Design has a direct and real relationship with conversion rates in this arena.
Design is important, and it's not always easy to explain why verbally. A handout for potential clients would be invaluable.