I have a few issues. First I have said that I prefer 1st edition AD&D many times and that 1st edition AD&D OA is my preferred form of OA- That is a lie. Looking back on it it is an unintentional lie. I started playing D&D with Holmes Basic, moved to AD&D shortly after and added in Moldvay's Expert set when it came out too. I don't remember the order of me getting the books and it's not really important whether I had the DM's guide or the Expert set first; the important thing is I have never played straight AD&D. Ever. I am also not such an old school purist that I am allergic to the good ideas from later systems. I like the way 2nd edition thief skills progress. I like 3rd edition's 3 saving throws and attacks of opportunity (in theory anyway, in practice they make players move in bizarre ways across the battlefield so as to avoid them).
In playing OA yesterday I am struck by some of the clunkiness of the system. The stuff I like about OA is great, the stuff I don't like about it kind of sucks and there is a bunch of stuff I am kind of ambivalent about. I like the classes (mostly) and the races. I like honor, but I think it could use an overhaul. I like families and ancestry and birth rights, they make for some interesting, if occasionally lengthy, character generation. I don't really like the non-weapon proficiencies, I never have liked the idea of using dice mechanics to handle social interactions and I don't like the idea of limiting a character arbitrarily because he hasn't taken, say, calligraphy yet. Many of these things could be determined by a characters background, which is why I liked secondary skills in the DMG. Some things should be fairly obvious by class- Barbarians probably all should have a shot at, say, fire building (as should probably everyone else only maybe at a penalty). Anyway, without ranting too much more here, most of the non-weapon proficiencies could be simulated with just an intelligence check or a dex check or a saving throw vs. whatever.
I really want a game that is a cross between Ruins and Ronin and 1st edition AD&D Oriental Adventures with a dash of later edition simplifying rules.
Birth Rights were kind of a pain in the ass for the first time ever in my experience. They need to be somehow tailored to class to avoid giving randomly wildly inappropriate things, like ninja weapons to samurai characters. I altered the item tables on the fly to give out more appropriate things, but it was annoying. Partial armor has got to go to. It just plain sucks to get something like a shin-guard of quality for your birth right. I intend to get rid of partial armors entirely. They can join non-weapon proficiencies on the scrap heap. For my campaign non-Japanese equipment needs to be weeded out since I am using a fantasy Japan setting.
Classes can be weeded a bit too. The OA Ninja as written (a split-class) needs to go. The Yakuza kind of sucks as written too. I understand the desire to have a "Thief" class, but they really don't work as a player character class. They make some decent NPCs though. The Monk I am not sure about. On the one hand they make more sense here than in "regular" AD&D, but on the other hand they made them more fiddly and complex with all the martial arts maneuvers and no one ever wants to play one anyway. I'd ditch the Shukenja, but the Sohei doesn't get spells until 2nd level like earlier edition Clerics- which is what they essentially are. Shukenja are kind of superfluous and apparently poorly named too since the Oriental "Wizard" class picks up that name in 3e. Wu Jen are just AD&D Magic-Users with some Asian flavors added, and are the only class not named in Japanese; I am all for changing their name to Shugenja and ditching the Shukenja and calling it a day for spell casters leaving them with the "new" Shugenja and the Sohei. For my beloved fighter types I am torn. The only reason I ever see anyone play a Bushi is because they didn't get high enough stats to be a Samurai, so I am tempted to go the Ruins & Ronin route of 0e D&D and just make on Bujin class, but the Samurai are the heart of every campaign I have ever run, except for one that was a 1-on-1 Kensai campaign. Kensai are cool, but need some work to make them really work. Not being able to use a magical version of your preferred weapon is just kind of lame, and the name should be Kensei, it bugs me that it is consistently misspelled throughout the OA book. Anyway, more research and brain-storming are necessary to fix the Kensei. The Barbarian is way more broken than any other class in OA precisely because it is, with only cosmetic differences, exactly the same as the Unearthed Arcana Barbarian, one of the worst munchkin classes of all time, topped only by the UA Cavalier (which the OA Samurai is a sub-class of but manages to avoid all of it's excesses).