It's a funny coincidence that all the features we want these days are things Half-Life have. 

 I wonder how many of us would switch over to Half-Life for modding if that ever got open-sourced.
How about this: Get in contact with the original Half-Life engine coders and ask them a bunch of questions, possibly revealing how certain things were done 
PS: Did I just hear Arnold's voice? 
PPS: I totally didn't know rockets didn't emit their own sound in Quake. I thought they did 
