Show Masterpages overrides.
There's no way you can tell that someone did alter or remove MasterPage-items on a document page. You should add a little + sign next to the page icon in the Pages panel. Just like altered Paragraph Styles.
This would be incredibly helpful. Additionally, if possible, I would like to see an option for highlighting or tagging the individual elements on each page that have been selected for "overriding" the master page.