Although this isn't only a submod for Sekigahara Campaign per se (it works with any mod), your campaign and setting was what originally inspired me to create this project!
Playing Sekigahara Campaign with "The Battle of Sekigahara" playing in the background just seemed too nostalgic for me to pass up! That is of course just the tip of the ice berg as I have meticulously added in tracks to fit all aspects of the game. If any players of Seki agree, you may find my little mod here:
http://www.twcenter.net/forums/showthread.php?t=551469