Ok.
You don’t seem to like the answers that you’re getting. So lets back up a bit and see what we can say.
OA is a brilliant, but confused book. It’s a set of rules, a setting, monsters, spells and classes that are contradictory by design. It was widely hailed as a brilliant book and didn’t win an Ennie because it wound up in the wrong category. (IMHO obviously)
The question you need to answer is:
1) Am I happy with the oriental part of my setting now?
2) Are the areas where I’m not happy going to be in OA?
OA has lots of great ideas, monsters, and weirdness. Even if you find Rokugan irritiating (and I do) it’s a novel setting that manages to get closer to the sort of fantasy-punk (samurai-punk?) you see in anime popular in the West than in any other setting that I’m aware of.
But its not like you –need- to have OA to have an authentic oriental-flavored setting.
If you have a strong image about the kind of setting that your world is going to be then it’s a question of crunch.
OA is a little-bit-of-everything book; in 3.0 it was must-have for the innovative mechanics. Due to its innovativeness at the time many of its best ideas have been shamelessly reprinted elsewhere (Taint, the base classes, spells, PrCs, etc) or else superceeded (basically the same list above).
So you have most of the best crunch elsewhere already.
If you’re looking to add OA-flavored weirdness (a.k.a. fluff) then you might be better off going out and getting something really weird or else more specifically targeted.
Not sure if that helped or not.