Awesome, sounds like you guys have made incredible progress. About the voice acting, have you guys considered recording the complicated scenes live and then sort of "overdubbing" with the final voice actors? Here's how I would envision it working:
1) The team member in charge of the VA, having identified the missions that require special effort, meets up with one or two enthusiastic prospective voice actors who have also read through the scripts beforehand. They discuss each exchange to get on the same page and then perform the missions, recording the important interactions as big single chunks of audio on a laptop or something.
2) The audio is packaged along with the scripts and uploaded to mediafire or whatever, and the list of parts that need to be filled is posted on the forum along with links.
3) The folks who wanna try their hand at VA can now download and mimic an actual performance that makes sense, has all the right little nuances, and isn't just them reading random sentences totally out of context. Even people who have never played the campaign will be able to turn in appropriately inflected lines with the correct pacing, tone, pronunciation of proper names, etc. They can then chop up and label their pristine, high-quality dubs and send them back in.
Clearly the major drawback is that you are adding in another step to the process, but the tiny performance group's efforts over the course of a couple afternoons would be magnified many times over by the individual actors, possibly yielding much more consistent and convincing final product. Plus they can go out for a beer or four afterward. Anyway, just a thought. I'm really looking forward to this campaign.