I'm toying with the idea of running a "swords and sorcery" fantasy game using FAE, and thought I'd throw my ideas for a magic system up on the wall for people to hurl rocks and garbage at.
First, an explanation: by "swords and sorcery," I mean a Conan-esque sort of game, where magic is rare, dangerous, and generally only used by evil sorcerers, cultists, and the like. The good guys may use magic, but either they're dabbling in relatively minor powers, or doing so at great peril to their souls.
My initial thought is to have a seventh, "Magical" approach, which I know has been discussed her before. My twist, though, is that fate points can't be invoked for Magical rolls. Instead, a character can swap one or more of his fate points for "doom points," which can only be used for Magical rolls. Spending a doom point will have some kind of downside, probably stress, which can be mitigated with consequences, which could be the social stigma associated with using magic, or the deal with dark powers that the magician must make to work his magic. Each doom point requires the character to shift one of his aspects to a "doom aspect," which can be invoked only with doom points.
Magical can be used to attack or defend, to create advantages (which could then be invoked for non-magical rolls), or to overcome. I'm probably going to allow overcome rolls to cause "effects", with a difficulty of 1-9 depending on the power of the effect.
The character can use the free invokes from scene aspects, from on advantages that he creates with non-magical skills, on Magical rolls, but once the free invokes are gone, he must spend doom points to invoke them.
Magical stunts would be used to represent spells that the magician is particularly good at or known for. For example: Magic Missile! Because I know the Magic Missile spell, I get a +2 when I use Magical to attack a foe at least one zone away.
The idea here is that magic has a cost--not only does it reduce the magician's "soul" as represented by his fate points, and his ability to act in the real world, as represented by mundane approaches, but using it brings pains of its own, in stigma, stress, and being beholden to dark powers.
That's what I've got so far; fire away!