Well, "extra weight on the class choice" is nice and all that, but having to play through the entire game with the class you're not really interested in mechanically/gameplay-wise, in order to see the ONE characters content is a bit too much. As for replayability, about the same can be achieved by, let's say, allowing players to choose which one of the optional characters will join their party and providing certain bonuses if said character aligns with MC's class. For example, let's say Azar is searching for a certain knowledge, and you need to get a certain grimoire from the local tomb/dungeon/market for her, OR if you're playing as a blood mage (a corresponding class) you can just impart that knowledge to her yourself (maybe even as an alternative quest?). Something like that.