I ported a large GUI app with comments entirely in Japanese once, so this oughta be easy. Also, it wouldn't be targetting MAME, I'd just want to hook it up in AO/AOSDK. And the lack of support for opcodes Sega doesn't use actually makes it simpler (less code to deal with).

Oh, and ZiNc has a fair amount of Polish variables and comments and I've handled it OK :-) PM me and we can set something up.