The Celestial Empire is not a fantasy tabletop role-playing game inspired by the myths and the history of Cathay, but a TTRPG firmly set in Imperial China, her culture, and her society. As a result, the rules as written strongly encourage the players to have a male character of Hàn ethnicity.
Now I realise this mayn’t be everybody’s cup of tea, and that today’s TTRPG public expects more diversity, both in terms of gender and of ethnicity, when generating their player characters.
However, having the GM set their campaign at the time of the Táng dynasty, and particularly in the capital city of Cháng’ān, could provide a solution. Under the Táng (618-907 AD), Cháng’ān, the eastern end of the Silk Road, was one of the largest metropolises of the world, a cosmopolitan city with several neighbourhoods explicitly designed to house the many merchants, pilgrims, envoys, missionaries, etc. coming from the lands to the West of the Celestial Empire.
This picture (from Twitter) shows the various ethnic groups one might have encountered in the streets of Cháng’ān under the Táng.
Note: the English-language translations in the yellow labels are from a Chinese Facebook group. “Rakshasa” is a wrong interpretation of the original “羅剎”, which used to mean “Russian” and which now indeed means Rakshasa [although I doubt there were any Russians in Cháng’ān; that is an utter anachronism].