Marty,
Having built the Carolina Central (based on you Kalmbach "book"), I have to say "thank you"

for getting me back into the hobby. Picked that book up on a lark but read it cover-to-cover multiple times and fell in love with the hobby again.
The only suggestion I have is to show some alternatives to the track plan you decide to build for the actual project. Using the CC as an example, I took your plan and modified it by switching to a 36 inch door, adding a third staging track, adding an extra siding or two into the middle, double-tracked the curve on the right, put the "front ends" of imagined "off layout" industries in each of the front corners and put a small yard between them in the front (yeah, I wanted more switching in case you couldn't tell).
Obviously there are infinite variations to any track plan but you could show just a few based on interest:
Looking for more switching? Consider this...
Have a little more room? Consider this...
A little squeezed for space? Consider this...
Want more mainline ops? Consider this...
You could also show (or discuss) variations based on era or scenery (e.g., desert vs. eastern forest).
If this book will be focused at all towards beginners or folks re-entering the hobby, this could be a nice feature. I've found in life that there are plenty of people who need some help "thinking outside the box" and a couple variations could help them with their "vision."
Thanks for helping me re-discover a wonderful hobby and best of luck on your new project.
nsauk