Just a thought to expand on. Warriors might add Bodyguard, Wizards with Magician, Thieves with Assassin and Adventurer's with Monks. More specific classes might make for a diversification of the various skill we have, and let us expand into new areas of expertise with it. More sub-classes could be added making it even more interesting.
The interface we currently use may not let the increase of skills work well, so this is one for the new engine when it is used.