maybe there could be like.. styles to the fighting, the fighters going more for offense, mages for evading, rogues for quick fighting, maybe two weapon fighting, maybe a monk class...

I'm not sure why you would want the game to force a fighting style on you. As an open RPG, the Eschalon series gives you the opportunity to use all sorts of fighting styles to fit your preferences and the situation. Why would you want the game to force a limitation on you?

Necroposting, but since the OP never answered the questions I figured I might.

Kreador, adding fighting styles to the game could be done in a way that wouldn't take away any character options, and could add more customization to your character.

The way I imagine it, when you create your character you would choose your axiom, origin and class, and then a fighting style. Your fighting style represents the way you approach combat and the equipment you typically favor. You might have 'Dual Wielding', that lets you equip two one-handed weapons at once. Most of the time you attack normally, but you have, say, a 15% chance to make an extra attack with your 'off-hand' weapon. If you want, you can still use a two-handed weapon or a shield and be just as effective as you would normally be.
For people who don't want to bother with the fighting styles, there could be a 'generalist' option that just gives you a flat +1 damage with all weapons.