Anyways, back onto topic, the problem with what your saying in the way life progresses is that you cant start a game as a very young teen, it would make no sence. How many games actually have age as a factor in them? Not very many. However what your saying has some point to it. It needs a little modifying but it could work pretty well.
During life you as a person and the people around pretty much have some idea where there going. Also the family they grew up in also is a large factor in what they want to become. ie. you want to be a doctor so you study a bit of biology, you want to be a lawyer you take law, your dad was in the army so during your entire life you looked up to him and wanted to be just like him. This isnt always true but these are just examples. So what im saying it have a few basic classes and the ability to pick from these classes.
Say warrior, mystic, and priest. Seem narrow? Really they arent. A warrior can become many things, he can find the light of god, become a theif, work for a king ect. The Mystic studies magic, he can aproach magic from many basic angles, be it nature, or holy, or even a dark art. The priest belives religion is the key, he perhaps feels that it is his duty to protect the word of god becoming a monk or even a paladin, he may feel he should preach the word and have god cover his back. The fact of the matter is, if you allow a character to branch 2 many times you get a mest up game unless properlly balance.
Here is an example. Lets say were playing mikes magic rpg of doomp, and pertend were a wizard. Throughout each level i keep gaining newer and newer spells from a variety of things. In the end i have all the spells in the game and can kill most monsters in under 3 hits.
Now think of the logic in this, who, in there right mind, and being human, would have enough time to study every form of magic, be it in the art of nature, the light or holy arts, the dart arts and so far. Perhaps what would happen is that you feel the art of nature is more of what you like best. So you start studying the basic fundamentals of it. You learn some basic spells from all forms of nature, water, ice, rock, lightning and so forth. Then you realize, wow, i really like how lightning works, so you begin to study the lightning form of nature magic, as study you learn powerful and powerful spells of these and the spells you allready know get more and more useful and stronger. No spell would be useless to you because whats the point of even making a useless spell? (ie diablo II, uhg some of the skills/spells, totally no point in having singleplayer or b.net).
Now the name mystic still applys to you but you are so much more, you are extremely skilled in the art of nature in the form of lightning. Sure, you come upon a monster who is immune to lightning in all shapes and forms, but there is where the \"P A R T Y\" system is usefull. It allows players to specialize and work together as a team.
As for a warrior, you belive that strength, your wits, and your will, in all situations will bring you through. Its a cruel world and if you cant stand up for yourself no one is going to. But lets say the whole \"law thing\" just aint working for you. You beging to not listen to anyone, look out for only yourself, steal things, you become in a sence a \"petty\" thug. Whether you continue down this path or not, it doesnot matter, what matters is the skills you learnt from doing this stick with you, so if you develope them further you become more of a skilled thief than a petty thug.
Well as you can see the whole \"class change\" thing really doesnt apply to this. YOU develope your character as in how YOU would think YOUR character would act in the game. You wana be a thief? Steal! You wana study magic? Study magic for gods sake! Belive in god? Become a priest!
Not saying that each basic \"class\" (warrior, mystic, priest) should be allowed to perform certain actions. It should actually be encouraged. How many mystic theives do you think there are? (well none now but its not a question to be answered :p) problem is there is almost no oppertunity to do that in any games that i know of prolly some. What im actually saying is that being a warrior gives u the bonus of starting with the basic skills to become a theif or a knight, and that the mystic has the basic skills to become a wizard or sorceror or even a druid, and that the priest has the basic skills to become a monk or a paladin or a shawman...
In this way each character can develope his/her own personallity...
Try to make sence of this i know it must be garbled.
And remeber! This is in all entirity \"MY\" opinion.
