There's one problem with this. Since everyone contributes with different machines and microphones and such, you're still going to get inconsistent results from your recordings. If everyone used the same recording setup, then this would be easy to do. Distance from microphone, type of microphone used, how it was recorded will affect the volume of the voice files.
I have two microphones, one a decent desktop mic that I splurged an amazing $20 at my radio shack for, which I used in Derelict. The other one I use which is one of those that come with webcams, the crappy little white stick mike (the tampon mike I call it) and when recording with both of those, I notice a drastic change in quality. For example, my own voice, with my desktop mic sounds warm, with bass and treble nicely balanced when played back. With the crap mike, it sounds like I'm inside of a tin can, thin tinny sound with no bass to my voice. If everyone used the same mike, and did the same post-proc to thier voice files, then we'd have consistency. Since it's not possible to do that, we just have to make do with what we have for our voice files.