Why does it make any sense that if you conquer somewhere the people will willingly join your army and fight their own people for a foreign ruler?
Also if you could recruit Korean soldiers then this would make the Korean navy useless because you would easily be able to resupply your armies.
During the Imjin war the Japanese conquered many major cities, including the capital, because the Korean army ran away.I mean sure during the Imji war the Koreans may have ran away from towns away from warfare, but it can't be all of them.
In 1907 Korea had a population of 13 million and in 1910 Japan annexed Korea. In 1938 about 3,000 Koreans applied to join the Japanese army and 400 were accepted, in 1943 300,000 Koreans applied and 6,000 were accepted, in 1944 Japan started drafting Korean soldiers because WW2 was going badly for them. Based on this in the 16th century it seems unlikely that a significant number of Koreans would willingly fight for Japan. Also it's unlikely that Japan would want soldiers who would rather run away than fight.If the Japanese conquered korea they will eventually recruits native Koreans in some lower class armies, there must be Koreans that would join right?
https://en.wikipedia.org/wiki/Korea_...bilization_Law
In theory it should be possible. Though as the skeletons are likely to be different I'd need something that could convert an armoured horse from Attila into something I could add to a S2TW skeleton.