I think letting users add Labels to the site would be a great idea, you’d just have to come up with a format for a label page. Labels listed on Album pages could be hyperlinked. Catalog numbers could be added as part of album metadata. Maybe a list of different releases of the same album on an album’s page, with the label and catalog number?
RYM, Discogs, and MetalArchives all have something similar, I’d love to see it on this site