that's a pretty map. Where did you get the bottom layer from?
I really like the sound of the fleet and walls rules.
Have you thought of adding a Barbarian power to the North? Seems to me like a good idea.
I'm concerned central powers such as Wei face too great struggles. Perhaps you can give those say one more unit...?
Neutral SCs should IMO generally be grouped in clusters. To create fertile battlegrounds.
In any case, please sign me on as an observer should you get a playtest underway.