It's a good (and pretty powerful subclass, one of the many from Xanathars that people will no doubt want)
IMO, adding DLC packs for new subclass packages inline with books would be a pretty neat way to do it. Base game covers PHB, then some packs for other player options. *shrug* There are a huge number of subclasses etc these days, so it's not like it wouldn't be a nice addition. Like a Xanathars pack could include a bunch of the spells, feats and subclasses found in Xanathars, a SCAG one could include the new subraces and subclasses found in that etc (plus the melee spell cantrips which are super important for fighter/mage concepts!).
