As a game system it could be interesting.
Some sort of Class Development and Path Choosing.
But, when it come to Sanctuary Lore, it wouldn’t quite fit.
In Sanctuary, the different classes are part of their own “tribes”. Of course, there are a few exceptions, but, for example:
Barbarians, Amazons, Witch Doctors, Necromancer, Crusaders… they all have world lore that supports the birth of their people, their “tribes”.
A warrior doesn’t become a Barbarian as a rogue doesn’t become a Amazon and a Mage doesn’t become a Witch Doctor.
But… not to say I just come with problems…
The system it self could be implemented in a more specific way.
- Barbarians, at lvl 25% (10/40, for example) chooses between… I don’t know… War Chief, Berserker and Chain Master (or what ever). Each one would have a few specific New Skills (1 to each kind, a whole new tab or whatever), that are exclusive to that Class Title.
It’s a smaller system compared to your idea, but would fit better the in world.
And, of course, it should be permanent…