Do you know that Asia means not only two Chinese Civil Wars? There was and is more than just Warring States and Three Kingdoms ...
This would be the same as saying Europe would be boring because only an English Civil War in the 17th century and various conflicts between Anglo-Saxon Dynasties in the 6th/7th century occured ...
Any TW game set in Asia could include many different nations with unique fighting styles. Just some examples I can think of at the moment:
You have the Khmer, Koreans, Persians, Turks, Vietnamese, plus various Malay/Indonesian naval empires, Horse-Archers like the Mongols/Xiongnu/Huns plus Burmese and Thai Dynasties using Elephants, various Indian cultures either Buddhists/Hindus/Muslims fighting against each other or Invaders from outside. Some Indian dynasties created even colonial empires by conquering parts of South-East Asia during the Middle Ages.
Furthermore you would have all the Indo-Greek, Indo-Parthian, Indo-Saka and Kuschan-Empires originating from Afghanistan and other parts of Central Asia penetrating deep into the Indian peninsular. Then there are the large Cities and Emirates in Central Asia (Buchara, Samarkand, etc.), when set in the 17th/18th century an Oman Empire fighting back the Portuguese in East Africa. And also in the later timeframes from the 16th century onwards all the european colonial powers as outside intruders like the Mongols in M2:TW and much more.
edit:
and then there would be spectacular and impressive battlefields. From the dryest deserts of Arabia and Central Asia to deep and nearly impenetrable jungles, the Highlands of Tibet or Mongolia, large mountain ranges and deep and dark valleys plus Mangroves on some tropical coasts hindering you to create a solid and stable battle line.
You have areas with tropical temperature the whole year to cold Siberia/Mongolia with 10 months of winter. Also heavy rain (Monsoons), sand storms, dense fogs and thunderstorms will feature you breathtaking effects and low visibleness during battles where you or the enemy can flank the other battleline and appear unexpected in your back.