The real world world isn't made of concrete. It'd be nice if there was a difference between the runways and the rest of the world. Running off the runway on takeoff should feel (and sound) like grass. Ditching on water should feel like water (and if your plane started sinking, even cooler). Related - force feedback effects for expansion joints in the runway, for grass, water and other surfaces, would be awesome.
Related related- if craters were more than cosmetic, cratering runways would be a good tactic. Possibly TOO good, if simpling bombing the spawnpoints completely shut down an airfeild. However if the craters didn't last long (and in reality filling them in was high priority) this could be quite fun. One way around the total shutdown of runways (as well as easy CAP vulching) would be to add dispersal pads, and the ability to spawn at them. And of course you can always take off on the grass....
Perhaps this is a bridge too far, but something to consider.
Related related related - if you take Google Earth to the Stanley airfield in the Falkland Islands, you can still see the chain of craters left by the first Black Buck mission, with the runway patched right where the last bomb hit it. Historical coolness.
