I don't think its feasbile to offer the breadth of fighting styles that many people seem to want within a single class. Unless, of course, the styles are represented as feats, in which case we're back to letting the fighter be the best possible hand-to-hand combatant just its the best at all other forms of feat-intensive combat styles.
Its not as bad as you might imagine- I did something like this in 2Ed. (Admittedly, it was easy considering that HERO 4Ed had a chart in its Ultimate Martial Artist release that allowed conversion of that games' martial arts maneuvers into D&D stats.) Honestly, there are all kinds of other RPG systems that have done this successfully- like GURPS and HERO- and all that need be done is think in a similar fashion.
It would require a little bit more typing on someone's part...but no more than a typical section of new Feats or Spells.
There would be a set core of skills in the class, but everything else would flow from player choices.
The Schools would basically be a combination of skills, feats and class abilities, tied together with certain benefits to membership in a certain School...almost like a prestige class within a class. The unique class abilities would be awarded like some of the various Rogue abilities.
While basic School features would be available to any PC willing to spend skill points or burn Feats, the innermost teachings - the unique class abilities- would only be available to class members. Like the current version of the class, certain feats would be available as bonus feats, but
which feats you could take would be limited by School.
So, for example, a practitioner of the "hidden" martial art Capoira would have skills like Perform (Dance) and Escape Artist as class skills, would have a Feat cascade of movement- related feats, and the weapons list would include small blades, manacles, chains and some other stuff. Class abilities might include flurry of blows (with combat & AC modifiers related to Perform (Dance)), Jumping bonuses, and so forth.
Someone proficient in a similarly "hidden" martial art, Escrima, would have similar skills, and feat selections, but would have short staves as weapons. They would also get the ability to improvise weapons with comparative ease, and still flurry with them as "monk" weapons, but their unarmed damage would not increase with level.
In contrast, a practitioner of Pankration would not have flurry of blows, but would have bonuses for grappling, and would increase HTH damage after a successful grapple. They would have no monk weapons beyond perhaps some kind of gauntlets. Instead of AC and speed bonuses, their HD type and Con might increase over time.