It would warrant a very serious change in the entire DM and GM, IMO.
As many would admit our AH DM was state-of-the-art many years ago, but is lagging behind the times nowadays. Therefore, implementing the actual effects of bullet hits that doesn't amount up to the total "destruction" of the specific part would definately be a step in the right direction.
Let's assume one or two a 20mm HE round impacts the rudder of a flying airplane - in AH2 this would not be enough damage to qualify as 'rudder destroyed', but in real life the explosive effects will have torn apart a considerable amount of the rudder as to make it much less effective than a fully intact surface. The same applies to a variety of situations such as ailerons or elevator surfaces.
But the problem is, our DM doesn't have much internal components modelled in, as well as our GM allows us to hit enemy planes approximately twice as much further out than real life distances - in some cases, even three, four times that. If partial damage and loss of effectiveness is to be modelled in without some revision in the general gunnery modelling and its effecting factors, then logically the game would encourage some serious spraying shi*. Just spray some ammo load out to the plane in front of you, and if it hits wing surfaces and such, it would cause more drag and deterr the effectiveness of the flight controls, making the target plane a much more vulnerable and easy target than it is now.
Therefore, if 'partial damage' is to be implemented, I contend that some more factors such as ammunition belting should also be modelled in - for instance, tracer rounds, AP rounds, and cannon rounds have different ballisitics qualities at further distances. Now, the ballistics don't matter much when firing range is very close, but when the distance is further out the difference does kick in.
Currently, AH uses a 'generic' type of bullet that has both AP and HE properties, and only the tracer rounds have different ballistics qualities. In other words, aside from every 5th round fired, all the other rounds have exactly the same ballistics.
Now, in reality, most on-board weapons had mixed ammunition belts, for instance the MG151/20 being:
* HET - AP - HE - AP - HET - AP - HE ....
In AH2, all rounds are generic except the tracer:
* G - G - G - G - T ...
In AH2, if you fire a MG151/20 at a target out at 600yards, and aim well enough to hit with the "G(Generic)" rounds (not counting the effects of dispersion) you will hit 4 out of 5 rounds fired, as all the "G" rounds will hit and the "T" round misses.
However, in reality, If you aim good enough to land a AP round at that distance...
* HET - AP - HE - AP - HET ....
..only two out of five fired will hit, as the HE and HET rounds will have different ballistics qualities.
In short, by modelling correct ammunition sequences to the guns I expect as much as a general 30~50% drop on accuracy in shooting over 500 yards distance. An added bonus could be, with a more refined DM the effects of different types of rounds (AP/HE) will draw some more variety in what happens in firing situations.
In this case, the "partial damage" would be a welcome addition.