That sounds like pretty specialised stuff, no wonder you got no response!
Its strange, I never gave thought to the audio side of things until now, and then suddenly you realise that its actually quite important.
Maybe we're looking at the wrong software altogether?! No, I'm sure theres a way out of this.
Have you any experience with a program called After Effects? I've heard people use this to make music videos so it must have audio support of some kind. I know Premiere has fade in/ fade out tabs for audio tracks, so if you were making a video you would have to manually adjust these to give the effect you're after.
Thanks for the info, I'll be sure to look into it