I understand the game is far from post processing but I was reminded to post while playing Supreme Commander. It'd be nice if shot down aircraft instead of always tumbling out of the sky, would sometimes lose altitude until they crashed into the relief of the land or exploded. Something like this: http://www.youtube.com/watch?v=Fko81Ji4 ... be&t=2m42s Although that entire video seems like great inspiration for destroyed aircraft animations.
I like the fact you tagged your post with [Detail], that's nice. Optimally, I think it'd be best if the aircraft crashed based on physics. If it gets hit hard on the wing, it should spin out of control. If it gets taken out by a light shot, it could glide to a crash. If it takes a heavy hit to the fuselage, it could break up in mid-air. I do, however, believe that varied "death" animations are an awesome but not necessary feature. This could even be a prime feature for a mod.
