Like I said, I wasn't sure about the established lore. If the written language of the Nords haven't been established I would love it to be based on Norse runes. They could have magic properties like the runes that Odin gained through his ordeal hanging from Yggdrasil, pierced with Gungnir in Norse myth.
Definetly, They could add a whole new magic system with the one already established. The norse did alot of Rune Magic they would Inscribe a rune such as the Z rune "eolh" which had the properties of protection, tell it what they wanted it to do and cut a finger and rub their blood across it. Not only the simple magic like that but also Ritualistic Rune magic could be added. It would be amazing.