My idea was for the release edition, of course a community fan addon could work to. But it would reach a wider audience if Larian studios was in on it, and promoted the effort, and provided the dialog text.
Prefferably it should be out of context to not ruin the game experience.

It would also be needed to have some experts of audio processing to clean up the audio.

The community could vote up/down the raw audio to get the best audio.

Not sure what you mean by not commercial?
If we would do this as a community effort, if we get it done before release we could give it to Larian Studios to include in the release. But then I guess it would be commercial or?

I do not want to pay people, but I suggest that the voices who get selected, also get into the credits of the game.