I think there is no magic here. If you want daily build images, then you have 2 options:
1) Always use ALL last version of everything 2) Use last metacello version. Someone needs to update each configuration.
3) copy a fixed set of mczs to a repository and use the baseline I thought that all mczs are copied to a let's say pharo 1.2 repository. In this case you don't need metacello versions because it loads the newest version which is always true. Well, it is always true if integrating fixes means that the changed package is put into that specific repository. But it doesn't seem to be like that so I have to read it again :) If the packages are taken from their own repositories than I don't see another way than to nail the version in the metacello config and update as soon as a package is updated. A tool like the browser will ease this step. Norbert
+1 for option 3) This also helps when a repository is down.