How would you go about running Oriental Adventures using a simple, BX D&D type system? That is the opportunity I'm considering. ACKS has a toolbox for building new character classes (in the as yet unreleased Player's Guide), which I plan to use to create detailed versions of the Oriental Adventures classes, as an exercise to get practice using the ACKS stuff. For now, let's look at them in a simple BX system. I'm using the LOTFP flavor of a classic D&D style game for reasons that will be evident.
In LOTFP, the fighter is the preeminent combat class, quickly surpassing everyone else in the ability to kill things dead with sharp objects. Samurai are represented as fighters with o-yoroi armor and daisho - the matching swords. If a player wants to tell me he or she is also good at calligraphy, haiku, etiquette, and performing the tea ceremony, that's fine. The game will be about stabbing monsters in the face and recovering loot like regular D&D, but we can make systems on the fly if a player feels the need to win a poetry contest or something in between trips to the ruins.
Ashigaru, the footsoldiers of the time, are fighters. Kensai, traveling masters of the sword - you got it - also fighters. OA has a class called "bushi" for peasant warriors, they sound a lot like ashigaru to me, but it doesn't matter, because they're also... fighters.
Warrior monks, sohei, and yamabushi were warriors dedicated to defending temples and monasteries. They swing weapons and kill things dead - they're also fighters.
Clerics in the setting are priests. I don't know that it really matters whether the primary religions (assuming a faux-historical setting) are modeled after Shinto, Shugendo, Buddhism, or something different; the setting will have Kami, a spirit world, and clerics are clerics are clerics. If a cleric player wants to call himself a "shugenja" because they saw that title in another game system, that's fantastic - shugenja are also clerics.
I'll just assume for now there are sorcerous figures in Japanese mythology and folklore like the Western archetype, and that'll be fine. I don't know where the inspiration for the Wu-Jen came from, but creating a d100 list of interesting taboos is too cool to pass up. Wu-jen are magic users.
LOTFP really shines for modeling thief characters in this kind of setting, using the specialist class. If you dress in black pajamas and kill people, you're a specialist. If you cover your arms in tattoos and work for the mob, loyal to an oyabun, you're also a specialist. The guys in the pajamas are ninjas, the guys with the tattoos are yakuza, and they both sneak around and kill people.
On a more serious note, the flexible skills in LOTFP let you focus more points into climb, stealth, and sneak attack, modeling the stereotypical ninja just fine; the rest is fancy specialized gear, and those black jammies that were popularized in movies from the 80's. The yakuza flavored-thief would focus a bit more on the other specialist skills, like search and tinker and sleight of hand.
The 1E Oriental Adventures book presented a couple of ideas for non-human classes - Hengeyokai, Korobokuru, and Spirit-Folk. I'm eminently lazy, and also don't get excited about designing classes and races, so the laziest approach is to take a virtual sharpie marker and cross out "Dwarf" and write in Korobokuru; replace Halfling with Hengeyokai; replace Elf with Spirit-Folk; voila, they run mostly like the BX or LOTFP equivalents - albeit with heavily changed flavor text, culture, and appearance. When I look at the ACKS class design stuff, I'll l put together unique race classes for these guys.
Other candidates could be 'rat people' - anyone remember the rat people ninjas from Magic the Gathering's Kamigawa block? Maybe it's all a big Ninja Mutant Turtle in-joke. But 'rat people' would be a good fit for the Halfling replacement - stealthy and difficult to kill - and it would leave the Hengeyokai as a monster race. I'd consider crow people too, ie, Tengu, but I'd also prefer to keep them as potential monsters.
I don’t think any new systems are absolutely necessary for using BX D&D or LOTFP in an Asian setting, but a pair of ideas come to mind, and I'm sure I'll be thinking about them in the weeks ahead.
First up is an approach to implementing honor or reputation. It was a big part of Oriental Adventures, and it seemed to be important to L5R, too. I plan on picking up Bushido and some of the other recommendations in the comments of the other thread, and seeing if any simple systems make sense to me. There's also a S&W game that went down this path, Ruins & Ronin, it may have something on honor as well. My expectation is that I'd use honor or reputation as another type of charisma modifier for reaction rolls.
The other one is martial arts. Regardless of the inherent coolness in sumo or jujitsu, I don’t see them moving the dial on a battlefield - and yet, early jujitsu did grow out of the need to disarm, trip, throw, and toss armored opponents and finish them off on the ground with a knife, the tanto replacing the misericorde of western chivalry. The player expectation is that ninjas and samurai and warrior monks will be able to toss people around with their mad skills when the need arises.
Just off the cuff, I'd consider treating unarmed attacks just like any other version of D&D, but using the pip system (2 in 6, 3 in 6, etc) to let a player roll a d6 when they make a successful unarmed attack; if they make their skill check, they can convert their unarmed damage to lethal damage (if using a hard style martial art) or add a kicker like a trip, throw, knockback, or hold, if using a soft style. It seems like that would be easy to implement and works with the LOTFP skill system. All of the amazing supernatural abilities you see in Kung Fu Theater (Eagle Claw! Dim Mak Death Touch!) would be omitted for now - no Shaolin Temples here.
I came to a recent epiphany on my approach to blending D&D and Horror; the ideas are still taking shape in my mind, but it would dramatically change my approach to Harrow Home Manor, and explain some things about the evolution of The Black City campaign.
I don't get excited about rules and house rules and minor tweaks; the OSR world is flooded with them, everyone has their own (like opinions), they're valuable and sometimes necessary, but just not that sexy. That's why my first approach is always, "How do I adapt something that's already built (like BX or LOTFP) and just use it in the new context?" Setting is our final frontier. That's the challenge here, to create a setting that works with D&D's tropes and expectations, but takes place in a fantastic version of feudal Japan. What a fun problem. First up: building up my library and getting in the required reading; my current "knowledge base", such as it is, comes from Kurosawa films and samurai cinema, Miyazaki movies, and a passing interest in martial arts (primarily judo and jujitsu). Time to get historical!
Edit: I thought of this after posting - didn't L5R have a 'rat humanoid' race? I don't have any L5R books, but that seems really familiar to me - I'll check it out when I get the chance.