Would this be a reasonable nerf to Annie or is it totally unnecessary?

Now, Annie is not a champion people usually complain about but laning against her today as Ahri made me think about her stun mechanic. Any champ that is laning against her and has no escape (or is too squishy) just cannot engage if her stun is up, that little bar alone is a strong discouraging warning (especially if her ult is up). It's a stun which she can keep up forever. Would it be reasonable to nerf her by implementing a decay time to her stun? Say, she hasn't used an ability in 10 seconds, she loses one bar, 10 secs more and she loses a 2nd bar, and so on. Or is this totally unnecessary? What would be the pros and cons of nerfing her that way?

As a mostly ARAM player I never gave much thought to her stun but laning against her made me really wonder.