Well I was thinking more along the lines of tabletop roleplaying games, where you can frequently mix and match classes to get the character you were going for, or even (in systems like GURPS) not have a class at all, which is kinda more like real life. At that point, you're not a mage, you're just an individual who has spent a lot of time studying magic and is good at it. Perhaps you studied other things too, but part of the idea is that people are different enough that a static class system doesn't represent a person's skill set particularly well.