For this to work it would take a huge overhaul of the system, particularly for your example above (CNJ+Fairy). I don't see this working from a balance perspective. I never played 1.0 but I believe they had something similar there where any sub could go with any class, forcing very specific builds because it is very difficult to balance this. Look at the original Guild Wars, they allow for any class combos, and they swing the nerf-hammer like they're Thor in a china shop.