Chris, I'm a GA class 2 EC. I have heard what you're sayig about being allowed to do the 400 amp houses with a class 1. I personally don't see why not, it's just 2 - 200 amp services in 1. However, my opinion is not the 1 that counts, you need to call the cheif electrical inspector for the county where the job is and ask for permission. I have heard that most of the time they will let you, especially if you regularly work in that area and they know you.
Personally, I think they need to change the classifications in Georgia to all residential and unrestricted. When they started licensing 99% of residential work was under 200 amps, now 400 and 600 amps are more common than 200 in my area.