I think some character themes might do this game very well. Concerning the music it does have very high production values, its clean and well put together, but what I felt it lacked was indeed personality. Out of the tracks I have heard so far they all fit the scenes but there was not much I latched on to or something that made me feel: I want to hear this again.
Character themes is probably a perfect solution, even a solo piano with some clear cut and distinct melodies will probably add that extra feeling. Such melodies, depending on how they are put together, could also fade in and out over other songs as a character has a specific moment.
I would also consider creating a strong main theme eventually, something to use for trailers and such. I would go full cathedral pop if I were you, a blend between organs and something like a classic anime intro. It would fit the blend of themes the game has as well and you could reuse melodies from the theme in key scenes. Just a thought.
Hopefully I will feel I have some time to read this summer, Earthsea will be put on the list. The Ender books has some religious themes running in the background of the narrative which you might appreciate , even though the author is a mormon and not a catholic. This is more apparent in the second book than the first. Among Atwoods works I think my favorite is the Oryx and Crake trilogy, it portrays a very specific and dystopian view of the future, but she is overall just an excellent writer, although her thoughts concerning things do not always align with my own.