Athene's Unholy Grail Buff Idea

So, trying to think of ways to buff in a way that makes it more appealing in general. Aside from my view that it needs +20 AP and -10% CDR, I was thinking MAYBE it might work to enhance the passive instead:

UNIQUE: Gain 20% of the premitigation damage dealt to champions as Blood Charges, up to 100 - 250 (based on level). Healing or shielding another ally consumes charges to heal them, up to the original effect amount. --> UNIQUE: Gain 20% **(+3% per 100 AP) **of the premitigation damage dealt to champions as Blood Charges, up to 100 - 250 (based on level). Healing or shielding another ally consumes charges to heal them, up to the original effect amount.

I think this would be a pretty alright change for AP midlaners who want this, as well as it might be a step towards letting AP supports make use of more AP heavy builds. Thoughts?