hm, as i understand it, there isnt even a proper port of chdk for the tx-1 yet, right? in german we have a saying that goes a little like that: "why talk about eggs that arent hatched yet"?
i'm sure the audio thing can be possible, but as it requires alot of calculations & modifications in realtime, this will be a hard task. we can barely use motiondetection at a speed of 50ms right now, for audio to be in sync, whoaw, i dont know. besides, the usb "logic" part in the firmware hasnt been found yet, only the "is there current or not" logic.
assumption: the day that is found the usb "logic", meaning chdk being able to "communicate" via usb port, will be the day people would want expanded remote-shutter capabilities, remote-capture, being able to transfer ALL kinds of files via usb (limited to jpgs, raws & sound now). that being said, i think the audio thing will have a low priority, as there is a) the aforementioned need of the people to use usb for extended remote-things and b) there only is a small fraction of people (among them, you) that would want that feature. i know, more and more people would want that feature as soon as it would be possible to be included, but i think you catch my drift.