Other thoughts:
A first-level hero shouldn't be Jackie Chan.
In d20 Modern, you've got the option of specializing and getting good at one thing early, or being a Jack of All Trades. You've also got some serious flexibility. You can really be any kind of Martial Artist you want.
If you want to be the typical anime martial artist, yeah, you could go Fast/Martial Artist. OR you could go Strong/Martial Artist, choose Athletic as your occupation, and take Tumble as one of your permanent class skills. While I love Jackie Chan and martial arts movies in general, I do sometimes get annoyed that everyone wants to be the Fast Hero in order to look cooler.
There really is more than just one possibility. Assume that every class here takes Athletic as their occupation -- that means that they can all get Jump, which is a Martial Artist requirement, and Tumble, which everyone takes as a must-have for a martial artist. As an athletic occupational person, they can also take Archaic Weapons Proficiency, which suits them pretty well when swinging ancient martial arts weapons, no?
Strong: This one is the duh. This is the martial artist optimized for damage delivery, and all other things being equal, he'll hit more often than any other character.
Fast: This is the martial artist who focuses on defense. He won't do as much damage as the Strong guy, but he'll get hit a lot less often, and he'll have more Skill Points to play with.
Tough: This is the martial artist who can get hit a whole bunch of times and still keep hitting back. With a bunch of hit points and the possibility of fighting on while at negative hit points or reducing incoming damage, this guy gets overlooked way too much.
Smart: Okay, not an immediate candidate -- he'd need to be a Smart6 before he could get into the Martial Arts class anyway, but just for fun, take a look at him: he'll have the option of using Exploit Weakness, Plan, or Trick, and he'll have a TON of skill points to play with. He won't be a damage dealer, but if you trick him out with the Defensive Martial Arts feat chain, he's still pretty tough to hit, and he could work as part of a group.
Dedicated: All martial arts masters seem to end up as Dedicated/Martial Artists. They attack decently, they get a not-lousy defense bonus, and they have that wonderful Improved Aid Another talent, which they can take multiple times. Or they could bump up their Tumbling, Balance, or Jump skills with Skill Emphasis and then later take Faith and Cool Under Pressure, giving them a little edge in combat.
Charismatic: Almost as unlikely as Smart, but just for fun, take a look. Forget Charm -- go with Fast Talk, Dazzle, and Taunt to be the guy who rattles his opponent in the fight, or look at the Coordination chain to help your buddies fight well as a team.
So there are your basic classes. As far as Advanced Classes go, I can see taking a couple of them for their benefits. Your average Ninja is gonna be, what, a Fast/Infiltrator/Martial Artist, right? The mooks the bad guy uses as his personal protectors are gonna have a couple levels in Bodyguard. And, frankly, for sheer killing power, the Soldier is the class to love.
Back when I tried to build my Ultimate Unarmed Combatant, I ended up with a Strong3/Fast1/Martial Artist6/Soldier10. The guy ended up with a great attack bonus and did, as I recall, 1d8+(some absurd number from strength, melee smash, and greater weapon specialization) + 1d4 from streetfighting, and had a critical threat range of 18-20 (martial arts feats plus soldier talents) for x3 damage -- and because he was a soldier10, he didn't have to roll to confirm a critical -- a critical threat was always a critical hit.
Was this guy the best martial artist ever? Doubtful. He was great for what I wanted him for, though.
The character I'm thinking about now is a Charismatic Martial Artist -- basically, I wanna make Elvis. (Elvis practiced Kenpo under Ed Parker and was actually much better than the cheesy choreography of his movies makes him look.)
-Tacky