Just read about the new source features in this release. It’s interesting, but I am not a fan of “pre-choosing” my preferences. I would like to be able to have the AllMusic reviews as my primary view, and have Wikipedia available as a secondary view, for all albums, all the time.
Given that, is consideration being given to using a dynamic “tabbed” interface for the information section of an album, in the same vein as “TRACKS / CREDITS / VERSIONS” that comes underneath each (current) album review?
Maybe I misunderstand what you are saying, but this is exactly how it works. You enable the sources you want to use, and then they are always offered. You can click the one you want so switch to any time.
(If a source does not have an article for an album/artist, is is not listed)
If you unfold the review, there is a list on the right with all sources that you have enabled. Click the one you want to read
If you enable many languages, the list can become quite long for popular entries if every enabled WP language has an article. I wrote a suggestion for this here, maybe your idea was going into a similar direction?