There are several skills that cover combative action: Martial Arts, Brawl, Melee, Archery, Firearms, Wrestling, and Improvised Weapon.
Brawl is the basic ability to throw punches and kicks. It is unsophisticated, and at the higher levels brawl is about inflicting maximum damage and it is brutal. It isn't elegant, and there aren't schools, methodologies or storied histories. Brawl cannot use the combo system.
possessed by: street punks, wanna be MMA fighters, bikers, Police officers
Melee is the ability to use a weapon in a trained fashion. It is like brawl, typically an unsophisticated mode of combat. It is mostly about how to use a weapon without hurting the user and in the modern age, how to not hurt your sparring partner. Melee cannot use the combo system.
possessed by: SCA members (sword), RennFaire participants, Fencers, Police officers (baton)
Melee as a Martial Art, it does exist. It has an elevated XP cost like martial arts and can use the combo system. The weapon becomes an extension of the fighter and some examples include Kendo, and other eastern disciplines that use weapons.
possessed by: ninja, monks, professional bodyguards
Archery is pretty straight forward. Archery cannot use the combo system
possessed by: SCA members, bow hunters
But Legolas, but Hawkeye! Archery can be bought like martial arts, and trick shots can be bought and worked into combat. It is limited though as drawing an arrow and nocking it is an action that has to be worked into the combo. Archery as a martial art allows the archer to use athletic move actions, use their bow as a melee weapon, and so on.
possessed by Legolas, Hawkeye, the Green Arrow
Firearms is a general combat skill, shoot reload shoot. Firearms cannot use the combat system.
possessed by rednecks, hunters, police officers, soldiers
Firearms as a martial art, as demonstrated in the movie Equilibrium, martial arts and gunplay can be welded into a functional hybrid. This functions the same as archery as a martial art, allowing the guns to be used as melee weapons, fired in combat, and mixing in athletic and acrobatic moves.
possessed by Clerics in equilibrium, Neo
Wrestling isnt the same as wrasslin, it is a combative art based around grappling. Wrestling can use the combo system. Professional Wrestling is a perfect demonstration of the Brawl ability. This is more olympic wrestling, grabs and holds.
possessed by olympians, some MMA fighters
Improvised Weapon is best demonstrated by Vin Diesel in the Chronicles of Riddick, and it basically the art of turning almost anything into a melee weapon. Upper case Improvised Weapon can use the combo system.
possessed by: Riddick, the Joker, Odd Job, Gambit
So there is an issue of combat balance. I'm not going to balance out the combat system, a professional martial artist is going to beat the crap out of a brawler or other non-professional fighter. Some combat skills are better than others, Brawl and Firearms are cheap combat skills, they don't cost a lot in terms of XP costs. Archery, and melee are archaic skills, so practitioners are rare, and the skills take time to learn. The martial art variants cost double the amount of XP and have a greater variety of moves, abilities, and access to combos. Does this unbalance combat in the favor of the martial artist? I certainly hope it does. Chuck Norris should totally be able to take out Hulk Hogan.
Does it unbalance the game? I don't think so. The martial artist is the pinnacle of hand to hand combat, and they should understandably be the best at it. The martial artist isn't unbeatable. Guns are a great equalizer. Can he dodge one bullet, that's fine we aren't shooting arquebuses these days, can he dodge 30? In the setting I'm using, technology is also a great equalizer: cyborgs, cybernetically augmented humans, power armor suits, tazers and lasers.