China is obviously a major power in the world (1/4 world population), and their crown jewel would ideally be Hong Kong.
We all know that recently Hong Kong was returned to the Chinese by England, but what if in this universe the Chinese took it back? The financial power of Hong Kong would make it a metropolis of considerable influence if any part of it remained. Personally, I would consider it the best place to begin civilization in Asia. With it being warm there, wet and jungle ridden, I can imagine a field of play that would be between Vietnam to possibly Japan, with priority given to costal regions. Going too deep into the mainland is REALLY hazardous to your health, especially with China being the primary source of America's Ire since they took Alaska.
In this game, I must assume that boats will become a really big part of the game, from river boats to steamer boats, and weather effects can on occasion include hurricanes.
Monsters are irradiated tigers and crocodiles and panthers and possibly elephants, with rideable versions of all of these. The Water Buffalo is the new Brahmin and so on. Roll around with an elephant gun, meet tribals out in the jungles and fox holes hidden in the ground. Stealth is a very big thing in this game, as is martial combat. Mountain Monasteries become small villages that ride above roving clouds of radiation and offer a life of the sublime which is constantly being challenged by NUMEROUS warlords and warring factions. There is no real power in China, for it has segmented down to numerous sub cultures. Think of the state of China in the movie "Hero" with Jet Li.
Complete and total government breakdown has occurred. There are no remnants to Chinese Government because the people by this point are so pissed off at the decisions of their government that they destroyed anything that was left. Whatever that was left hid themselves in various bases around China.
A possible faction would be the Japanese... largely untouched by the bombs, Japan might be the only technological force in the area.
Another Faction might be the Oni, essentially the "Demons" made of Ghouls and Mutants
The Remnants, Leftovers of the Red Army that managed to not degrade into tribals, warlords or similar, are found to the north.
A final faction might be individuals who were Americans that got stuck here. Their base is a beached aircraft carrier (South Korea area)
This idea is large in its infant stage, and any other thoughts and suggestions would be more than welcome, but I can imagine that Stealth becomes a remarkable focus of this game. The term more human than human also comes to mind in a multitude of low-level augments. Minor gene-splicing, minor cybernetics, minor chems... all together with martial study and perks can make a person that is truly a one-man army.
Landscape ranges from desert (hemmed in by the Sea of Glass, an area of desert that's been turned into an endless sea of beads of irradiated glass) to the north, to towerign mountains laden with rice patties and monastaries, to teeming jungles and finally to the urban sprawls of Hong Kong and possibly Tokyo.
DLC content might include More of Japan and parts of the Philipines, and Vietnam if it can't be included in the first place.
Thoughts/questions everyone?