This is truly an excellent guide. Great job!
There is one optional shortcut I would suggest concerning UnitModelTypes. Unless specific clothes/armors/weapons are to be designed with the new race or there is a necessity to grant or restrict access to certain items, I think it saves a lot of time to use preexisting ones. Say if one were to design a new magic oriented Kingdom race, using the models of a similar race (AmarianMale/AmarianFemale) would be the easiest way to go. That way it is possible to skip updating the (nightmarish) art defs. Just a suggestion for the lazy ones among us.