I think it would add more of a challenge to a pilot in the middle of a fray who gets his props shot up. not the engine, but the prop independently. there are stories of it happening all the time in WWII, where a pilot had a hole in one prop, as well as a cannon round logged into it. it caused the wounded to really suffer in aerodynamics, and shake violently.
so, what if we made the damage model so where the engine and the props can be damaged seperate of each other, and when the prop is hit, the plane starts to shake, as it does when you are overstressing the airframe in an attempt to reach the sound barrier

also, when enough rounds are shot into the wings, the plane should become heavy on that wing, causing it to roll to that side a little, as well as cause aerodynamic problems. again, to add more of a challenge (of course, im air-to-air challenged as it is!

)
just something to add even more realism
