Yeah I get it...just a misunderstanding on my end.
On the contrary...how would such a system of taking the vital part off/getting the kill be? I think it'd work pretty good...after all the one who takes a guy's wing off is the one who 'killed' him.
The problem with that scenario is our current "binary" damage system (either destroyed or not).
For instance :
Pilot A fires into a P-38J at a high deflection angle. Quite a lot of .50 cal hit. The hits take out 2 of the 38's MGs, pilot wound, left engine, left flap, left Aerilon, nose gear, left gear, puncture fuel tanks, and left rudder and elevator. The P-38 bugs out and tries to head for home. Obviously this plane isn't going to be the easiest to fly, and quite unable to perform much in the way of combat maneuvering.
On landing approach, Pilot B comes along, sees an "easy kill", and lands a 30mm tater into the already heavily damaged left wing, and the P-38 crashes into the ground destroyed.
In the current system, Pilot A gets the kill. If the rule applies of only "vital part = kill", then Pilot B would get the kill. Which pilot deserves it more?
Another example :
Pilot A lands a couple of 13mm and a 30mm tater on the backside of a F6F, appearing to only damage the aft fuel tanks (but in truth, heavily damages the aft fuselage, vert and horiz stabilizers). Pilot B comes by and hits the F6F with a snapshot of .303s and the entire tail of the F6F comes off.
In the current system, Pilot A would get the kill for the heavy damaged caused by their strike. In the "Vital part = kill" system, Pilot B gets the kill. Which pilot deserves it more?
Just a couple of scenarios to think about.