With a post-1521 POD, have the Wokou (the so-called "Japanese" pirates) found and/or take over independent states in the China Seas.
Lots of bonus points if they somehow manage to conquer a country that actually matters, and not something like the Ryukyus.
Lots of bonus points if they somehow manage to conquer a country that actually matters, and not something like the Ryukyus.