That would need the Gokturks, Sogdians and Tibetans. 
My idea is a historical campaign about An Lushan Rebellion.
Prince Li Heng (Chinese) swears regaining the country land back and wiping the rebels out.
The main objective is to defeat 2 opponents located in the northeast, An Lushan (Chinese) and Shi Siming (Chinese). Their allies, Gokturks (Gokturks) and Sogdians (Sogdians) have several spawning points, keeping helping An and Shi and raiding the player’s base located in the southwest.
There are 3 secondary objectives.
To liberate the capital Chang’an located in the central west from An’s troops to the ally Tang (Chinese). Tang would train the troops and join the battle after it regain this biggest city on the world.
To protect the 3 TCs of Tang located in the south and southeast. Tang would regularly contribute the resources if its villagers can keep working. This one would be tough.
To choose the help between 2 allies, Uyghurs (Tatars) located in the northwest or Abbasids (Saracens). Pay 2000 gold to Uyghurs for gaining the Silk Armor, Parthian Tactics and Hussar upgrade, then Uyghurs would train some Keshiks, steppe lancers and cavalry archers to join the battle too. Or, defeat Uyghurs to gain Zealotry, trading fee down to 5% and regular contributions from Abbasids.
My idea is a historical campaign though. 
The player would lead the Jurchen tribes located in the central of the map, must decide to be allied with either Liao (Khitans) located in the west or Goryeo (Koreans) located in the east within 1 minute. After making the decision, the ally would contribute a plenty of resources to the player for starting the game.
The main objective is to destroy the wonder of Liao if allied with Goryeo or the wonder of Goryeo if allied with Liao. If not allied with anyone, the player have to face both of them as opponents and to destroy the wonders of them alone. But the Jurchen pirates (Jurchen) would become the ally automatically and give the resources.
The secondary objective is about the Jurchen pirates.
If allied with Liao, the player could also be allied with the pirates and pay 500 gold to it in exchange for sending raiders to Goryeo, or destroy its 2 bases located in the north and south to defeat it and grab its resources.
If allied with Goryeo, the player could only choose to defeat it and grab the resources. But Goryeo and the Japanese would give the player extra resources and techs to express their gratitude.
If fighting alone, the player could only choose to be allied with it but it would automatically fight against Goryeo and Liao as long as it does not resign.