Stupid idea: Remake Rageblade
Rageblade now grants 35% hybrid penetration rather than a stacking IAS/AP buff.
Voidstaff and Last Whisper are both removed from the game.
One of the big issues with Void/Whisper is that champions don't really have to sacrifice anything to buy it since it helps destroy soft and hard targets alike. Now most of the worst offenders are forced to sink gold into a stat they don't need if they want one of the most powerful sources of damage amplification in the game.
Obviously this would be a buff (or a net-neutral change) to a number of hybrid champions, but they could be brought into line with targeted nerfs if the situation called for it.