I have another suggestion for modding entire nations. When I first started working on my nation (Haida Gwaii), I opened a Dominions 2 nation mod called Ashikaga Shogunate and basically copied the structure of this mod by Potatoman while making my mod.
The way Potatoman formatted that mod is similar to what order the modding command sections are listed in the Dom3 modding pdf. So I was able to just follow along with his mod opened side by side with mine and know exactly what commands I needed to use to make units, weapons and the nation specific functions.
Without using an existing mod as a reference, it would have been a nightmare to try to structure the mod with any semblance of order. The modding commands for Dom3 are alot more varied and complex, so once I was finished with the core part of the mod which is similar to dom2, I just plugged in areas for starting magic sites, spells and other new features where I felt appropriate.
So my final format looks like this:
1. Mod Info
2. Weapons/Armor
3. Units
4. Commanders
5. Summons
6. National Heroes
7. Pretenders
8. Existing Pretenders
9. Spells
10. Magic Sites
11. Nation
I hope maybe some of this information is help with your ambitious project.
