My first instinct would be to create a whole new base class for the martial artists. Possibly one to replace the Monk, which I've always had issues with anyway. But... I don't really think new classes are necessary. As others have pointed out the Fighter fits the bill pretty well... or could with some very minor enhancement.
I would go with a selection of new feat chains, as others have suggested. This would allow anybody to know a little bit, while a Fighter that uses his or her many feats to climb the chains a true martial artist. This would work well for unarmed martial arts. You might get away with a few feats for the armed martial artist (which I think is a perfectly valid argument) but the existing combat system and feats take care of this for the most part.
I would go with a selection of new feat chains, as others have suggested. This would allow anybody to know a little bit, while a Fighter that uses his or her many feats to climb the chains a true martial artist. This would work well for unarmed martial arts. You might get away with a few feats for the armed martial artist (which I think is a perfectly valid argument) but the existing combat system and feats take care of this for the most part.