IcyCool said:
If you prefer, you could have different damage types deal different amounts or types of ability damage.
Beat me to it...
But, yeah... just have ability damage be one of the "effects" applied after HP damage. In addition, you can keep whatever other effect is called for from your critical chart. A blow to the head might do INT or WIS damage in addition to stunning (or whatever). A smack on the arm might do d4 STR damage and render Shield Arm useless. Healing the STR damage will remove the useless arm penalty, and gives you an easy, measurable way to tell
when the penalty is removed.
Of course, not
every crit should result in ability damage, and some should be less severe (a single point.) And in some instances, the ability damage would be the
only effect. Adjust the crit chart accordingly.
The rules for ability damage sound like they mimic the length of time you (GoGo) want to reflect for "naturally" healing broken bones, and there are already rules for spells curing it. Also, the cleric would have to have it memorized for it to be used during combat. In addition, using those spells (Restoration, Regeneration, Raise Dead

) means that's one less higher level "cure" the cleric can use, which is a reasonable trade off.
Little off topic: The "Best of Dragon" magazine collection coming out next month is suppose to include the classic "Good Hits, Bad Misses" critical hit article from a couple of decades ago. Should be very interesting to see how that one's updated to 3.5.