If LoG is treated like a full LoN addon faction then it would have full access to the rest of the LoN stuff. Lady O will be a Deathlord and thus have access to all spell lores. The Legion will have its own traits and items as well I would think. Grave sites, LoN allegiance plus sub Legion traits.
Im curious what this means for the other Legions. Will they have full access to all Nighthaunt units as well? Battleline will probably be unchanged with the possibility of 'battleline if' situations