Currently once a discID is removed, it's really really gone, and hard or impossible to recover without knowing the actual disc TOC.

It would be nice if these were retained instead.

For example, I expect it would be relatively easy to copy their attached release's tracklist to a CD stub and hold the discID there. This way it is safer to delete discIDs without losing data.

This was brought up in http://beta.musicbrainz.org/edit/26840567 and http://forums.musicbrainz.org/viewtopic.php?id=4885