New Defensive Item: Gem Plate

So I was browsing items today, and I noticed there isn't a lot of AP and Armor stacking items. In fact, there are 3 available on Summoner's Rift, one is the armguard and the other two build off it- Zhonya's and Moonflair. These items are more for an AP champ looking for extra defense. So, why not an item for a tanky champ looking for some AP? Here's a concept for an item that would provide tanks with some more ability power.

Gem Plate 1250gp Build: + + 250 gp Details: +75 Armor, +40 Ability Power, Unique Passive: Gain +5 bonus Armor and Ability Power for each nearby enemy champion.

Not just precious stones, I bring you an ancient power.