AOE2 Forgotten Asian Kingdoms / Empires

Despite AOE2 already has 35 civs, I feel that there're still some important civs missing. Since I'm most familiar with Asian history, I gonna talk about Asian civs. This thread is purely for fun, as it's highly unlikely that the devs would want to add new civilizations.

In my opinion, there're two important criteria when selecting a potential new civ. First, this civ must have had interactions with at least two existing civs. And secondly, this civ hasn't really been covered by existing civs. For potential Asian civs, I noticed that many people have suggested Khitans, Jurchens, and Tibetans. I think Khitans and Jurchens have already been largely covered by the existing Chinese or Mongol civs, I can't see how one could make them different or unique. Tibetans, on the other hand, are a perfect choice, but could potentially get the game banned.

Considering all these factors, here're the four missing Asian civs that I suggest as potential new civs, and they all fit nicely within the current AOE 2 time frame, which spans roughly from the mid 5th century with the fall of the Western Roman Empire to the end of the 16th century with the Imjin War from 1592 to 1598 and the fall of the Burmese Toungoo Empire in 1599.

The 4 missing Asian civs:

Nanzhao (738 - 1253), representing Nanzhao and its successor state Dali. They had existed independently in the southwestern corner of China and the northern parts of mainland SE Asia for more than 500 years, and was an important regional power. They had interacted with the Chinese, the Burmese, and later the Mongols.

Tanguts (late 9th / early 10th century to 1227), mainly represents the Xixia Empire (1038 to 1227), but also sort of covers the surrounding Tibetic peoples. They started off serving as mercenaries for the declining Tang Dynasty, and as a reward the Tang gave them a plot of land in northwestern China, and also gave them the surname Li (Tang royal family name). They had developed a unique culture and a unique script that were different from the Chinese, and they had interacted with the Chinese and the Mongols. With the Tanguts added, I think they and the Mongols could share a unique set of Inner Asian architecture that is different from the East Asian one. I honestly feel that the in-game Mongols having Japanese / Chinese style architecture is quite awkward.

Champa (192 AD onward). They had already existed before the onset of the AOE 2 time period, and was fully absorbed by the southward expanding Vietnamese (which by the way should be re-named as Annamese to fit in the time period of AOE 2, since Vietnam is a name that appeared quite late in the 18th or 19th century) as late as 1832. They were culturally and ethnically distinct from the Annamese in the north, being followers of the Hindu religion and speakers of an Austronesian language. They were quite influential in the medieval maritime trade from China to India, and interacted with numerous other civilizations including the Malays, the Khmers, the Annamese (Vietnamese), the Chinese, the Indians, the Saracens, and the Mongols. They had a sizable fleet and would often engage in piracy, raiding the unsuspected merchant ships passing by their waters.

Siamese (13th century onward), mostly representing the Sukhothai and Ayutthaya kingdoms, but also covers kingdoms such as Lan Xang and Lan Na. Some people might consider them to be almost identical to the Khmers, but the fact that they spoke a different language (Tai-Kradai instead of Austroasiatic) is enough to warrant the creation of a separate civ. And they had interacted with numerous other civs too, most notably the Khmers and the Burmese.