I believe that relics of the Charm type should be usable by both Nobility and Charm clerics.
Currently, the Nobility domain is only capable of using Law relics. Charm relics could offer a degree of versatility without disrupting the theme.
I've admittidely got a bit of skin in this game, but from firsthand experience: maybe consider at least the possibility of making at least a few more "Type: Charm" relics "Type: Charm, Nobility" so they're usable by both?