AD on its own is a blunt instrument because within the scale of the ships involved in the game, a Ka'Bin'Taks primary weapon would be orders of magnitude stronger than the Sho'Kovs, but it is abstracted down to make it a reasonable number of dice to roll.
As it currently stands, a given single hit from a fighter (without Weak/Precise) has exactly the same probability of knocking out the engines (1/6 crit) on a Sho'Kov as it does on a Ka'Bin'Tak, and that makes sense does it? Personally I think not.
This is why I think essentially making critical effects modifiable by the PL level of the firer makes sense - certainly no worse sense anyway than the status quo.
Primary weapon, maybe (if we're talking heavy laser, for example). But not necessarily for other weapons.
When talking about pulse weapons, for instance, the light ion cannons mounted on a
Ka'Bin'Tak-class Superdreadnought aren't necessarily substantially more potent than the ones on a
Thentus-class Frigate.
It's just that the superdreadnought carries a hell of a lot
more of them.
There's no reason why a single ion cannon turret of pretty much the same design should be harder to destroy on one ship than another - the difference is that on the capital ship blowing off one turret should only take out 10% of the firepower.
Critical hits of the -1 attack dice variety reflect this well - with each battery on the Dreadnought being 10 attack dice it could take a lot of AD penalties before being rendered unable to fire.
The trouble is, as said, the 'All' criticals - 4+ roll on all weapon, one arc taken out entirely, etc, etc - do scale up.
In terms of raw damage, a damage multiplier weapon is better than lots of AD (since a double damage weapon loses 1/12th of its firepower to bulkhead hits, not 1/6th), and since critical hits get damage multiplied as well, there's nothing lost there.
The problem is not in the damage, though, it's in the critical hit effect - what's been pointed at several times is that a single damage critical will blow out a ship's engines just as fast as a quad damage one. Admittedly, the quad damage critical will blow away a much bigger chunk of the ship at the same time, but on a reasonably tough ship, you're still more screwed by multiple weaker criticals because the odds are you've lost more systems.
The problem is threefold:
1) you might well need a fairly significant redesign to include anything like this. Which is not going to be forthcoming in the near future.
2) it becomes quite record-keeping heavy - games like Full Thrust and B5 wars divide up the broadside weapons into an appropriate number of boxes which are lost bit-by-bit but do require a proper ship control sheet and quite a lot of note-taking. Since A Call To Arms is meant to be a fast system to play, that can be a problem.
3) More than once various Mongoose Publishing Staff have said that they like the idea of being able to get the 'magic bullet' critical. Which means that even if they get reduced in occurance in some redo, they're not going to go away.