I think Civ in East Asia is still too scarce. This region has an extremely large historical record and shocking historical stories in the Middle Ages, and various ethnic groups also have a large number of empires, making it suitable for the emergence of new civ
Adding the following Civ would be better: Jurchens, Chiang, Khitay.
The coverage of these ethnic groups:
~Jurchens: A fishing and hunting ethnic group located in northeastern China in the late Middle Ages, active from the 10th century until today and later known as the Manchu people, with Manchu language passed down from generation to generation.
~Chiang: The ethnic group in western China that implemented the entire Middle Ages, represented by the Tibetan and Dangxiang ethnic groups, has been active since the 5th century and the representative language is Tibetan.
~Khitay: A nomadic people located in northern China in the early and middle Middle Ages, some say descended from Xianbei and disappeared with the rise of Jurchen and Mongolia.
The countries represented by these ethnic groups:
Jin Dynasty (1115-1234 AD) - Jurchens
Qing Dynasty (1616-1912 AD) - Jurchens
Tibet (633-842 AD) - Chiang
Western Xia (1038-1227 AD) - Chiang
Liao Dynasty (907-1125 AD) - Khitay
Or perhaps choosing Tibet as the new civilization is also a good choice, as the Chiang are too broad.