Hitachi EX120-5 Pattern Control Changer

I have a grey market EX120-5 with a 4 position Kawasaki brand pattern control changer installed. Position "Y" is standard "Cat" control but the other three K,M,H are Asian standards we don't see in North America. I would like to modify it so one of the positions is "John Deere" style. Is anyone familiar with this pattern changer and attempted any modifications. I'd be happy if I could find a schematic showing the hydraulic line layout or access to a parts book. There are some letters stamped...

Hitachi EX120-5 Pattern Control Changer

Hitachi EX120-5 Pattern Control Changer