First off, before I begin, I will offer a caveat. I believe in modifying cultures to fit the needs of the game and the setting, not the other way around. To that end, what I would be doing with the Orient is nothing that countless writers have not already done with the Occident. As we all should know, D&D is not a true and historical approximation of medieval or Feudal Europe in any sense. If it were, you would not have adventuring bands scouring ruins for treasure, you would not have sentient nonhuman races with their own societies interacting with humans, you would not have wizards casting magic (they would be burned at the stake in the true medieval Europe), you would not have anachronistic types of weapons and armor existing at the same time, and so forth. Writers have not adapted the setting or the game to make an accurate simulation of European culture, but rather have borrowed elements of European culture to fit into the setting and the game.
Hence Oriental-based cultures will necessarily undergo many of the same types of changes. Dwarves, elves, gnomes, halflings, orcs, goblins, and other humanoids all exist alongside humans-as with humans, these races exist around the world on every continent. However, like their human counterparts, the demihumans and humanoids have their own cultural variations-halflings may alternately occupy high ranks in a given social structure due to their skills in agriculture and farming the land, whereas dwarves are actively courted in feuds between human clans for their skills in metalworking and their prowess in combat, as well as their strict adhesions to oaths and their lawful behavior.
The social structure does exist, but it has more flexibility than you might imagine. Feudal Europe was often a very stratified society itself, with little upward mobility, as we see with peasantry, serfdom and the ideas of noble and aristocratic bloodlines. Yet, in spite of this, adventuring bands can and do contain people of different races and social rank-so too is it for an Oriental setting. Oriental societies will be more stratified, to be sure, but adventurers by their nature often operate outside this social structure or tend to upset it, and so those who have been disgraced or suffered a loss of position, or who otherwise wish to improve their lots in life, will choose the adventuring path.
The question of honor and feuds is an interesting one-if this is too heavily emphasized, one may question whether a person will ever say or do something that could be construed as dishonorable or that could provoke a feud. One thing that struck me as odd in the original OA adventure was the presence of wako, or Oriental pirates-shouldn't they be acting honorably as well, or is this just something for the PCs? Do NPCs ever insult people, either not caring or even hoping that their words will provoke a vendetta or a feud? How do these conflicts start if everyone, PC and NPC alike, always acts to avoid provoking feuds or dishonor?
Please note that not all of this is meant to dismiss the very real differences that Oriental-inspired lands will have from those inspired by Europe...but it IS important to avoid the double standard of bending and stretching European culture to fit the needs of the game and the setting, while insisting on stricter authenticity to Oriental culture. The object should not be to strictly reproduce the culture-we don't do it with Europe, so why should we do it with the Aztec Empire, Ethiopia or Rwanda, Mongolia or Japan, or any other non-European culture that existed at the same time as Feudal Europe? To be sure, there will be differences between different parts of the world...but there will be many common links, including the presence of orcs and elves worldwide, the same rules governing magic, and so forth. How different parts of the world interpret and react to these tendencies will vary, of course, but they all inhabit the same world and must all abide by its rules. Just as the Euro-inspired parts of the setting will by necessity react to the presence of real, actual sorcery and sentient nonhumans that can be interacted with face-to-face, so too will the parts inspired by the Far East, Mesoamerica, or Africa.