Rage is not about fighting skill. It is about losing oneself to anger. The main reason it is not mindless kill-frenzy was for the Barbarian class to be playable. Also Lawful characters do not make a habit of flying off the handle in combat. Raging is a honing and eventual perfection of emotion surpressing reason and rationality.
As Mousferatu said in the first reply to this thread, alignment restrictions are entirely about flavor.
Suppose I invented a new ability for monks that they get instead of their first two bonus feats. I call it
Offensive Ki Focus. It is about ignoring dangers to one's person in order to focus all your mind into dealing powerful blows and being able to temporarily sustain wounds that would kill a normal man. It requires intense concentration, which forces it to only last a short time and leave the character fatigued afterward. A monk that becomes non-Lawful loses the ability to attain Offensive Ki Focus.
Offensive Ki Focus A monk can attain a special offensive state of mind a certain number of times per day. In offensive ki focus, a monk temporarily gains a +4 bonus to Strength, a +4 bonus to Constitution, and a +2 morale bonus on Will saves, but he takes a -2 penalty to Armor Class. The increase in Constitution increases the monk’s hit points by 2 points per level, but these hit points go away at the end of the focus when his Constitution score drops back to normal. (These extra hit points are not lost first the way temporary hit points are.) While in offensive ki focus, a monk cannot use <insert a flavorful list of skills dealing with self preservation> He can use any feat he has except Combat Expertise. A state of offensive ki focus lasts for a number of rounds equal to 3 + the character’s (newly improved) Constitution modifier. A monk may prematurely end his focus. At the end of the focus, the monk loses the offensive ki focus modifiers and restrictions and becomes fatigued (-2 penalty to Strength, -2 penalty to Dexterity, can’t charge or run) for the duration of the current encounter (unless he is a 17th-level monk, at which point this limitation no longer applies).
This ability is virtually identical to rage, but now flavored for only lawful characters.