Idea 1: Alignments as trust networks
Detect Evil doesn’t make someone glow red. The paladin or cleric just says “trust me, that person is evil, kill them.” And why do you believe that guy? Because he’s lawful good? How do you know he’s lawful good? Because he says so, and he’s part of some well recognized religion which says “this is what’s right and wrong, we’re lawful good, trust us.”
(Note, a later commenter has pointed out that in Basic D&D, at least, the Detect Evil spell did cause things to glow. Too late, though; I’d already been inspired.)
Idea: Cyberpunk setting where society has degenerated into something feudal and strongly influenced by fantasy gaming, with sufficiently ubiquitous wireless networking that netrunners are very like wizards. Alignments are basically just mutually exclusive trusted-key networks, possibly affiliated with social organizations, like religions, bunds, corporations, or franchise nations.
Still missing: A reason for the various alignments to be exclusive. Because if they’re not, they’re not alignment-like, are they?
Idea 2: Memory-palace magic
Idea: Wizards need to set up memory palaces to do magic and memorize their various spells and arcane formulae. Players actually map out their memory palaces, noting which areas relate to which magical abilities. Magical combat consists of invading someone else’s memory palace, which involves using the map for tactical combat. (Possibly Diaspora-style social combat.) Assuming Fate rules, maneuvers can place Aspects on a zone in a memory palace, which can then be Compelled later on whenever the wizard tries to call upon that zone for a magical effect.
Could maybe be adapted for an Inception-like game?