Fabio Milito Pagliara has also provided an Old School for the contest, this one based on material from AD&D 1e Oriental Adventures.
Thinking about it this could be a perfect way for many things, among others martial arts, I would take lead from Oriental Adventure AD&D 1st edition (this is an old school post after all) and bend it to the concept presented here :)
I have toned it down a little and put only “easy” to rule maneveurs (no choking holds/locking parry ecc)
Kung Fu (Hard-Soft style)
Kung Fu is an ancient martial arts learned in dojo, monastery and from traveling masters. Renowed in the area are the Dojo of Master Fei-Lon (in the big city, double the cost, need to convince the master himself to be a worthy student), on the mountain nearby there is the isolated Monastery of Shang-Ki a lesser deity of the zone (LN, fight honoraubly, perfect yourself, protect the weak) where student will be accepted if the swear to follow the teaching of Shang-Ki. A renowed if strange teacher is the (in)famous Jack Lee a peerless master (Fighter 11th + all 10 lesson of this school) but with a strange curse (must get drunk each day before sunset) so while he is an incomparable fighter it’s quite complex to follow him… to be accepted as his student you must drink with him….
- My body is a weapon: you can combat without weapons whit no penalty, your attack (kick, punch , knee) do 1d6 damage
- defense: in combat you have AC 8 
- expertise of attack: you can do 3/2 kung fu attack each round
- expertise of defense: you have AC 7 
- mastery of attack: you can do 2/1 attack
- mastery of defense: you have AC 6 
- Iron Fist (attack does 1d8 damage)
- Flying Kick (need a running start only attack does 3d6 damage. if attack fail fall prone)
- Iron Skin AC 5 
- Missile deflection (make save to deflect missiles – arrows, bolt, sling stone ecc)
Simple, straightforward to apply, what’s not to like? May be taken by fighters (warrior-monks), clerics (sohei?), magic-users (this might be unusual, but I admit I like the idea of a mid-level wizard having a 1d8 punch).