OK, I see what you mean.
I'm not sure that there would be any real benefit to this though, as far as I know, the metadata for avi's is limited to a few basic bits of info such as the title and copyright.
What would be ideal is a new container standard that allows the media file to contain the same info as the nfo files, maybe along with posters and backdrops. This is way beyond my capability, and generated little interest when I brought it up over at XBMC. But maybe one day.