Cassock? Mortarboard? What is that?
Álvaro Semedo, a Portuguese Jesuit priest in China at the end of the Ming dynasty:
Nicolas Trigault, a French Jesuit priest in China around the same time:
Though a Protestant should know not to trust the Jesuits, in this case the Jesuits made a sensible choice, to adopt Chinese dress in China, specifically the dress of Chinese Confucian scholars. Two centuries later, Protestant missionary Hudson Taylor made a similar choice to adopt Chinese dress, much to the chagrin of his English missionary colleagues.
Even though the everyday clothes of ordinary Chinese are much more Westernized today, the everyday clericals worn by Christian priests and deacons ought to reflect the native meaning system in clothes, rather than shout FOREIGN. For this reason, something like the above, analogous to English cassock, gown, and college cap, is what we should come to expect in China of even priests that are come to serve from overseas.