Oh, I'm always a big fan of Manichaean PODs, however in order for this one to take off, the Hongwu Emperor would have to convert to the Light, and since the man was always keen to be seen as a defender of Confucianism, and Neo-Confucianism in particular... Maybe instead one of his sons could take a more direct interest in Manicheanism than their father did and become Emperor, the man had A LOT of children, there are plenty of alternatives to the Jianwen Emperor and the Yongle Emperor.
The key thing though is that the Manichean Emperor KEEPS the Dragon Throne long enough to affect the level of authority to not only declare Manicheanism the State Religion of the Middle Kingdom, but I assume you want it to stick for a while.
Though in the long-term I can see Manicheanism being treated as a variation of Buddhism by the local population and traditional animist religions of China will change it.
In fact I could see a future with another dynasty having to do a balancing act between traditional Confucians, Daoists, Buddhists, and the new fangled Manicheans who have it clear that they are not going to role over and die.