new item for critical strike /dmg?

in assassin rework you created few items that looks awesome but i really would like 3 rd item in IE essence reaver option that would fit to champions who dont need AS but want crits. i mean something like this : saber of true assassin 60 AD 30% critical strike unique active : after 3 seconds(2 for meele) your next AA will deal 200% AD TRUE DMG. 30 - 15*critical strike chance seconds CD. this active can be cast only in combat with enemy champion or epic monster(they take 50% DMG)