The most basic option for a stunt is to allow a skill to do something that it normally can’t do. (FC89)
But can an aspect do that too? Aspects are supposed to be permissions for certain types of action.
Let's say I have a character with the Unbound Psionic aspect, and it's been established narratively that he can use his mind to generate psionic barriers that are strong enough to stop bullets. Let's assume further that an opponent is shooting a gun at him. As his defense action, can he use Will in place of Athletics to defend against this attack?
At the risk of sounding subjective, is it okay that this is his preferred method of physical defense, given that Will is his highest skill?