Most RPG's that I have seen have a traditional stat system that the player increases in various combinations to boost his/her character for a chosen class:
- Strength
Dexterity
Charisma
Constitution
Intelligence
A very crude example is if my AC is higher than my BC then I could be classified a warrior...if my BC was higher than my AC then I could be classified a Hero or something to that effect. As stated it is a very crude example so there is no way it will work...
Weapons could then provide bonuses to a list of classes.
Also if this game were to ever have any sort of magic system there would have to be additional stats implemented, which then could be configured in to something like this that would allow for other classes.