...hmmmm....
Black Shield can be used on your allies aswell, right? Would the successful blocking of a CC on your ally apply to your proposed passive aswell? If so, what strategies could this open up, and does it affect the balance of Morgana?
That aside, your passive seems like a great proposal. The first thing that came to mind is the fact that she will no longer have an innate source of sustain, though. Would that affect how she plays? How much of a negative effect would it have on her earlygame? Stuff like that.
Anyway, Ame, I wish your luck in your appliance for the internship! If you're still going through with it.