I've unfortunately been a little behind on this thread, and now the wiki is eating my time to the point where I got 5 hours of sleep last night and haven't eaten all day because as soon as I got out of class I went straight back to wikifying RPGWW. My enthusiasm for the wiki is absurd.
Anyway, there IS a system that does what you're talking about, and it's called GURPS. In GURPS, taking damage means you take a penalty equal to that damage on your next turn to DX and IQ, which basically penalizes everything you can do to continue fighting or defend yourself. GURPS is a very simulationist system, and getting hit in a duel often means losing straightaway. Realistic? Sure.
But I think it's too harsh for the more cinematic Philsys.
I'm not sure what a super-crit is, but I am guessing you're talking about the double-crit where you beat your opponent by 30. That happens so rarely in my experience that having a rule like that that applies only to double-crits is unnecessary.
Nama actually proposed an admittedly way more complicated version of what you're talking about--critical blows should not only deal additional damage but penalize the target in other ways. Both ideas have suggested that getting your ass beat should shove you back in the init order, possibly opening you up to a follow-up attack. The penalties are cumulative and possibly long-lasting in both variations.
I like the idea conceptually, because it's neat, even it it could get complicated. I don't like the idea systematically.
Critical hits are a function of randomness; more often than not a crit has more to do with a good die roll than with the attacker actually having a base AT or whatever 15 points higher than the defender's PA. The wider the margin between attacker and defender the larger the chance of a critical blow, but it's still functionally luck.
PCs must, over the course of their lives, face many, many adversaries. The average PC will fight dozens of enemies and usually emerge victorious (as it should be, not that it should always be easy). If a PC scores a critical blow to finish off a hated foe and is able to follow it with another set of attacks that obliterate the target, it can be very cinematically impressive.
If a lucky crit from a minor enemy has the same effect on a PC, most players are going to feel incredibly gypped.
Most NPCs that see combat are intended to do so only once. They will fight the PCs and ultimately lose. An individual NPC will fight far fewer PCs than a PC will fight NPCs. Statistically speaking, an individual PC is more likely to suffer a critical hit than he is to deal one to a specific NPC.
For example, Lady Deeum might have to fight her way through a horde of kobolds (say 20). If her chance of scoring a critical hit is 1/4, she will score critical hits on 5 kobolds. Those kobolds will probably die horrible deaths. But even if the kobolds have half her fighting skill and score critical hits only 1/8 of the time, Deeum will suffer about 3 critical hits. For Deeum, a heroic PC, her criticals mean death to one of many potential adversaries. The criticals by the kobolds mean she's getting her ass beaten, maybe even dying after the first blow, and there's only one of her!
This is an obvious reason why one person is foolish to take on a large army, but that isn't really the point. The point is that increased randomness favors monsters and is disadvantageous to PCs, because over time, monsters have many more "chances" to "get lucky" and score a deathblow critical hit. In general, I'm not in favor of rules that increase the power of randomness for this reason.
And that's my comment. <p>