I still think Bard would be best added through professions. Professions in general could use a revamp and made to add more combat-viable utility and 'Profession flavour' to the game.
We're seeing the inclusion of a Bow and Quiver that grants Dark Ranger effects, it opens up the possibility of crafting items and item enhancements that add the same properties.
Leatherworking patches could be imbued with a special properties like Glyphs, where it's opened up to a variety of Class-specific abilities. Engineering could open up Class-specific augment options for gloves, boots, belt and back pieces. Having these tied to professions and have them affect your Class ability like Glyphs would make it more feasible to maintain different RP identities, on top of the Transmog systems we already have. It'd be a better way to incorporate Musical and Engineer themes straight into the classes.