Someone pointed out that mages in Fate of the Forgotten Realms can still begin play unfairly overpowered – consider the following: a wizard with a Scholar rating of Great could start with four magical stunts (meaning, possibly: twelve signature spells), and four bonus character aspects in the form of available schools of magic.
That’s too much. Just rule that no Player-Character can begin play with access to more than two schools of magic. Also, if a player takes the Dabbler in Magic stunt, rule that they cannot take an extra magical stunt until a major milestone has been purchased (or awarded).
Finally if any spell proves particularly impactful – place a material cost on it’s use, owing to rare and/or expensive components: anything from 50-100 gold pieces is reasonable, or more depending on the status of Player-Characters in your campaign – a powerful spell or ritual could easily cost a thousand ‘dragons’ in addition to the mandatory fate point, “Sorry Mrelder, but powdered rubies and dried yuan-ti scales don’t come cheap – anywhere in the realms!”.
It’s never too late to retroactively apply these rulings – just have the player swap out one stunt for another using the guidelines above. The Dungeon Master’s Guide has been updated to include the rulings detailed here.
Finally, as an aside – consider stunt utility. Players want to use the stunts available to their characters. Try not to narrow the focus of a stunt too much, there should still be clear parameters set but if the conditions under which the stunt becomes available rarely happen then the stunt never gets used: compare the wording of the stunt Hardcore Parkour here (under Professions), to how it’s detailed in the Core System.