> I tried the following from the 0.8 live CD with a HD mounted on /mnt/hda1

That's what live-snap shot is doing now.

> Wouldn't it be neat to have modules containing data and/or
> executables that can be added to or removed from the system at
> runtime?

Yes, refer to [issue650], http://bts.grml.org/grml/issue650, for the
patch. 

closing it since it refers to obsoleted unionfs, instead of aufs.