Armed Devices like Levantein and Graf Eisen have an odd quirk that deserves mentioning.
Gigant Crusher, for example -- is it a spell that Vita can cast using any weapon, is it purely a function of Graf Eisen's Gigantform, or is it somewhere in-between?
The same question applies to Laevantein's Schlangeform and the Schlangebessein attack, and the Bogenform and the Strumfalken attack.
Revolver Knuckle is another Armed Device which might have attacks built into it: Revolver Shoot, Revolver Cannon and Knuckle Duster, punching attacks that rely on the spinning compression-gears.
"In-between" possibilities include:
(1) The Devices were designed with these features in mind, but required Signum and Vita to learn the spells to activate them. Fans of the Exalted tabletop RPG should think of this in terms of the "Evocations" that artifact weapons will have in Third Edition.
(2) Signum and Vita had already learned how to magically create/manipulate metal, such that Signum can extend any metallic weapon she wields and Vita can enlarge/extend any weapon (as well as create metal bullets; Vita would thus seem superior at metal-magic, whereas Signum diversifies with fire magic). Their Devices are merely designed to make this metal-manipulation magic more efficient.