Just some ideas after talking with some gaming buddies:
Different magic users. For a campaign with multiple magic types (not just Path/Spellbound). I'd love to see an effects based magic user, or something like an Elementalist from Skulduggery Pleasant (I'd argue that the Adept is actually pretty well suited to the 8 specialists in many ways, but I could see it getting it's own unique treatment, too).
It'd be nice if they demonstrated clear differences in their approach and use in various scenes compared to a Mage (or one of the 8 specialists) who uses a static list. The Mage requires less dedication, because you can rote learn a single spell, but is like a "lazy man's way to power" compared to an effects based user who has to master the concept behind the effect - sort of longterm power, but harder work.