I used Oriental Adventures 1st Edition to bring martial arts to the campaign. One character was a Kensai (if you're not familiar with that, it's essentially a weapons specialist) who chose martial arts as his specialty. He was initially the only PC kicking ass, until another player with a fighter asked if he could learn that cool stuff.
Normally, a PC needed to find a master to train him, but I didn't see any reason why the Kensai couldn't train the fighter if he wanted. The way it works in 1st edition is that all you need is an open weapon proficiency slot- once you fill it with a chosen martial art, you get the armor class and basic damage of the art. (You also get multiple attacks, but I overruled this in favor of characters using their usual table for multiple attacks as they progress in levels. This makes for a better balance, otherwise characters get too powerful at low levels.)
When you get more weapon slots, you can fill them with special maneuvers which cause more damage, or give the PC more defensive capabilities. (ability to dodge arrows, or a flying kick which can cause triple the base damage of the style, for example)
The Kensai character had more abilities than the regular fighter because of the character class, but the regular fighter was still a force to be reckoned with. (I mentioned this character before in the post about the "ones" tables. This was the same guy who lost both swords off the tower by rolling a "1" to hit- he was still dangerous unarmed.)
For me, it just makes for far more interesting combat when fighters are doing more than just swinging swords.