Me, I'd like an 'internal model' and an 'external model'.
Since we already receive engine/oil/rad damages, I guess there's an 'internal' damageable part in the game to some extent... but IMO it could use some more parts. For instance, in IL2/FB there are some more interesting levels of damage.. like the supercharger being busted, or the throttle control system stuck.. the control cable/rods cut.. and etc.. makes out for a lot of interesting situations.
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But what I'd really like more than anything, is to see the planes with internal support structures.
In IL2/FB, one interesting point is that the differences between the weapons are very clear. In that game, it is very unlikely to cause a catastrophical structural failure with .50s.
The .50s usually cause fires, engine failure(radiator, supercharger, engine oil), control failure(aileron/elevator/rudder cable/rods cut).. and the pilot is in most cases forced to bail out from his plane. If you put in enough .50 rounds to actually saw through the internal supports, the chances are, the plane would actually explode before the wings or tails snap off - since it is much more likely the .50s snag a fuel tank before it "saws through" a wing spar/section with multiple rounds.
On the other hand, cannons of 20mm and above literally blow pieces off planes, which is much more likely to cause structural failures, before any damage is done to the engine or control systems.
This makes an interesting tactical difference between the planes. Planes don't go down immediately with .50 fire... but the chances of ruining some very vital, internal component is much higher than cannons, not to mention the .50s are easier to hit with. Also, fires happen a lot more commonly with concentrated .50 fire - no doubt, the incendiary rounds are doing their trick in IL2/FB.
In case of the cannons, they are harder to hit with, but cause more damage upon impact, and a concentrated burst will bring down a plane immediately, by ripping the control surfaces off.
I don't know if AH2 has that kind of internal DM... but I don't think so. If it does, then obviously it's not enough.
Now, the 1C: Maddox guys took something like 5~6 patches and about a whole year to get the feel of it right... but once its done, it really shines - well worth the effort, IMO.