Up to now, there hasn't been anything remarkable about the suggestions I've made for distinguishing weapons without varying damage. Someone, somewhere, has done each of those things, although perhaps not in such an explicit manner.
Special abilities are a little different. Occasionally, you'll see a note that gives a flail a percent chance of disarming an opponent, so the concept is definitely out there, but not unified. My own approach to special abilities, like disarming, entangling, and the like, is to think of it as a risk for the target: the opponent rolls a d6 and compares the result to the damage roll; on a match, the opponent is disarmed, entangled, tripped, or whatever the weapon's special effect is.
In some cases, a weapon may have an ability that takes effect when the damage roll beats a target number or a d6 roll by the opponent; this can be paired with a more serious effect if doubles are rolled. You can even have multiple special effects on doubles: on double 1 through double 5, one ability takes effect, while on double 6, a more severe ability takes effect.