An additional Unique Passive for Black Cleaver

Just an idea:

Would it help Juggernauts, Divers and Skirmishers (basically, sustained combateers) if got the following named Unique Passive added?

Unique Passive - Last Whisper: Grants X% (for instance, 10%) Bonus Armor Penetration against targets with full Cleaver stacks.

As this requires application of full Cleaver stacks first, it should keep Black Cleaver less attractive on assassins. And, having the same name as the Last Whisper upgrades, it would not stack with those, either. Obviously, this could help Cleaver users tackle tanks more efficiently in sustained combat, without making it too strong against general non-Armor buyers. Meanwhile, for ADCs, Last Whisper Upgrades should remain more effective.