I respect your intention, but I have seen this before...many times. Even played with similar rules (actually, practically identical).
Eventually, questions started getting raised "How can a fire attack smack someone in the face?"...So we developed a chart for fire attacks. Then some started complaining "How can I cause a head injury against something bigger than me?", so the charts became locational, then the question was raised "But shouldnt higher level abilities have greater influence on the outcome?", so now critical factor variants were introduced, then the question became "If a critical factor variant for power X is applied to a leg attack, but its psycic damage...why did I get a bleeing wound in his gut...?"
One round of combat took could take HOURS because of the rules and counter rules and table lookups!
Then you have the whole aspect that you have focused on weakened, slowed, dazed and stunned in the consequnces, creating an artifical shift toward gear and abilities that directly counter these effects
If you really want to make criticals more exciting, try building more feats that effect crits, or gear with more interesting crit effects. Allow players to base effects off crits (like a feat that can stun target when crit with a mace or hammer when using an encounter power...). It remains consistant with 4e design in general (which doent use a hell of alot of "chart reosolution") and allows more interesting critical to manifest through character growth
If charted crits for you, good luck. But for my part...been there, done that, know better.