No less so than shield extenders. It would mean you actually have serious drawbacks to armor like you already do with shields. But of course NOBODY wants armor to be balanced with shields.... well..... at least not the armor tankers.

How do you armor tank?

Should be 5% for all plates.
Giving interest to Complex Plates.
And Ferroscale.

The Hp value is already too high.
(Once the unbalanced weapons got nerfed.)

Plates should not be the "default" choice. I need drawbacks.
Speed players should not be able to fit plates (even basic) without real penality (2% come on...)

Reactives should cost same PG/CPU than regular plates since they have 1/2 of hp value for 1/2hp/s.

The reason armor tanking became way better than shield tanking is because they both buffed the armor-per-plate and gave a reduction to the speed penalty. On top of that, there were very few options for anti-armor weapons. One was a sidearm, one was a heavy-only weapon, and one was a situational support weapon. Now that two mainline anti-armor guns are around (RR and CR) armor tanking is closer to being balanced with shields, but it's still not quite there yet. Perhaps we shouldn't return it to it's old values (3,5,10), but we should increase the penalty to the point that shield suits are adverse to running them but the armor suits still benefit from them. I suppose that means putting them at around 2,4 and 8. The basic plate is in a great spot since new players get it first and need as much of a bang for their figurative buck as they can get. 4 is more than the enhanced penalty currently is, but still isn't as bad as it used to be. 8 Seems fair for the complex, however I think that the complex needs another 10~20 HP on it so that it's worth using. The point isn't to gimp the plates after all, it's to balance them.

Just to be clear, we need a jewelers mallet here CCP, not a sledge.