What the new 120 ap item needs to be

After playing on the pbe with the new 120 item (which was removed if I remember correctly) I felt like it missed the mark by a mile. Damage wise it wasn't bad. If you hit 4 champions you would do over 800 damage late game. The problem is that 200 of that damage is most likely hitting a tank, who simply shrugs it off. It just didn't seem to make an impact. Mages have a lot of outplay potential(well at least some of them) and the next 120 ap item should be something to add to that. If you look at ad items, mercurial scimitar, Blade of the ruined king, even hydra can help you outplay your opponent. Mages need an item that makes them more dynamic. The zhonyas hourglass is a perfect example of this. It offers you the ability to outplay a lot of champions, maybe too well but that's another discussion. I know riot wants to stay away from actives(which i truly and honestly disagree with) but they make the game much more dynamic. The new item needs to be just that, dynamic. One of my friends suggested an interesting idea for the item. He was thinking about an item that when activated gave you a 5 second boost of ap at the cost of 20% of your maximum mana (the cost could be health, resistances, mana was just the one that made sense at the time). In the middle of a teamfight you could activate the item and use as many of your abilities as possible. You would have to really manage your mana before and during the fight which would be the main draw back. If the active cost health, your could build a seraphs embrace to essentially cover up that loss of health. Another idea for a 120 ap item could have something to do with qss, but I haven't placed too much thought on that. I'd love to hear what you guys think and have come up with yourselves. Right now I would just really love to see a more dynamic 120 ap item.