Writing a design doc is NOT easy. I spent most of the time working on it so far rewriting and rearranging what little I've done. I think I now get what you're supposed to present and how to present it. It hard to know what you're supposed to put in each section, what the sections are, and what to put in at all. I've sort of just decided to throw everything in. If there isn't a section made for something make a new section and flesh it out later.
I have a list of technical problems that I'm going to have to write small test apps to figure out. For one I have to figure out how I'm going to render the models. I'm going to have to render the faces of each poly and then render the lines which make up the pseudo-wireframe seperately. I'll have to figure out which methods look best.
Also since most of the military units will be able to move their turrets etc I have to figure out which method is best to represent independant objects that are linked together.