Medieval Japan will make a fantastic setting for a mod - good luck!
The Sengoku period is a great choice but the 10th-14th Centuries (Revolt of Taira Masakado, Gempei War, Mongol Invasions, War Between the Courts etc) are, if anything, even more suitable with the emphasis on heroic individual combat, horse archery and clans composed of small warrior bands.
You have scenarios like the Taira clan making its name crushing pirates of the Inland Sea and the adventures of Minamoto Yo****sune and Benkei.
Anyway, that would be another mod so I'll shut up...