A new bruiser ap/armor item that wouldnt be abused by tanks

So riot wont make an armor item with ability power because tanks like and so on would abuse it. Well i am a main and i would love to be a bruiser with her rather than an assasin so i thought of this item which could also fit well with possibly even without being too overpowered for other ap mid champions.

the item would be

stone gauntlet +15 armor +40 ability power +250 mana +30% attack speed (maybe?)

builds out of

passive: gain +1 armor for every 8 ability power you have. (caps at 50) your auto attacks deal additional magic damage equal to the bonus armor this item provides from ability power

Now the reason this wouldnt be good for tanks is because it would provide only 20 armor (+5 for the 40 ability power it has) and if they wanted more they would have to build items with ability power taking away from their tankyness and causeing them to be ap bruisers instead. In order to gain the 50 armor from this item you would need 400 armor which is pretty much unobtainable for a tank.

The reason ap mids wouldnt want this item is because most of them are casters who wouldnt benefit much from a mesely 40 ap and attack speed

Now there is a champion who would abuse this but maybe they could tone his late game damage down to compensate if he became a problem?

Overall i think that this item could be a healthy addition to the game providing that this is a late game item and if you built it early game it would barely do anything for you