I agree that it can be made, but I don't think that is a good move at this stage, because not all classes are implemented in the game, thus they are not fully balanced at this point. If we go on the road of multiclass before we have balanced our current classes and specs I think that would break many of the classes.
After the game is published and classes are optimized, that can be made as a separate mode/server/realm.
And also since you mentioned warrior mage, we have some pretty cool ideas for the classes and they won't be generic, you can count on that, think about battle mages with swords, exorcist priests with cross-bows and interesting stuff like that š
That's true, I suppose that with sufficiently original subclasses/specializations, multiclassing is not very necessary. In any case, thanks for your attention