I know this is a pretty drastic change, but I think it makes a lot of sense. Wizards (Arcane), Clerics (Divine) and Druids (Primal) are all prepared casters. Sorcerer, whose casting list is based on blood line is prepared. This makes bard stand out as unusual. Furthermore Bard and Sorcerer are both CHA casters so if you want to be an occult caster you much be spontaneous and CHA based.
They seem to be moving slightly in this direction with the esoteric scholar feat, but from a game design point of view I think this would put the 4 types of casting on equal footing.
