Not a bad idea, I'd run the plan by Hitech before you put in too much effort though. The shape probably isn't too important as long as it meets the guidelines he has laid out. One of significance is that no country have an advantage by virtue of layout. This kinda requires that the field setup be symetrical, unless you can convince him otherwise.
You may want to build a smaller terrain to get very familiar with the editor before starting a large one. Learnt this one from experience.