Um...the voice files are in OGG already. The file extension by itself doesn't tell you anything about the bitrate of its encoding, or any filters that may have been applied to the original audio. For all we know, increasing the quality of these files could double or triple the final VP size.
As for "very young voices," surprise surprise, but a lot of people who play this game are on the younger side. We have a very limited pool of potential VAs here; it's basically whoever feels that they can make a decent recording and has the will to sit there and say/re-say dozens of lines. It's not like we can go out and ask Crispin Freeman or Steve Blum (and if you don't know those names, you need to watch more good anime dubs) to record some lines for us. It's an entirely volunteer effort, and I have a great deal of respect for the skills of quite a few people in our community. Let me make this challenge to you: if you think that you'd be able to do a better job than the people who submitted lines, then why don't you let us hear how you'd have done it?
As for all of these people you've supposedly talked to, by all means, get them in here to post their feelings. Come up with some specific parts (or even specific lines) that you feel aren't up to snuff. If you're suggesting doing something as massive (and ultimately time-wasting) as re-dubbing an entire campaign, you'd better have some damn good evidence to suggest it. As a pre-emptory rebuttal, I spent some time going back through the voice VPs, and there were several parts in particular where I thought the VAs did outstanding work (and no, I'm not taking myself into consideration in the least either way). So...let's hear it, then.