I saw where a Redditor did this mod here: http://imgur.com/a/URCTy
 
And now I want to do the same, but I was hoping that it would be possible to use the existing jack as the mic output rather than wiring in a third. Could anyone verify if this would be possible?
 
Here's a photo of existing jack and the board it's soldered to: https://dl.dropboxusercontent.com/u/75755/IMG_20141121_222527.jpg

Take a look at the cable that plugs into it. If it is TRS, then you gave one channel for left, one for right, and one for ground. You need a TRRS cable so that you have a channel for your mic.
I don't understand the board, but basically as long as you follow TRRS convention and wire your mic and drivers accordingly, you shouldn't need the board at all. I might be wrong though, as I have never done anything like this. I'd be interested to see how it turns out though.

So I finished up my mod. It worked and here are the results. It seems like the 8323's might've been designed to be a headset originally so this was a pretty simple process.
 
https://dl.dropboxusercontent.com/u/75755/IMG_20141124_000434.jpg
https://dl.dropboxusercontent.com/u/75755/IMG_20141125_191447.jpg
 
I think it came out nicely all in all. It's the only fully modular headset that I know of so that's pretty cool if nothing else. Also, the audio quality doesn't seem to have changed, which I'm really happy about.
 
If anyone wants to know what I did, I basically just moved the wire that was attached to MIC to GND, then soldered my jack to GND and MIC. There's already a nice recess in the center of the cup that fit my jack perfectly, so I just drilled a hole there to mount it. After that, all you need is a TRRS cable, a TRRS to 2x TRS splitter, and a mic.