When the discussion comes to mass change of page labels, advice is always given in a way, which might be appliclable in a sandbox with direct administrative data base access.
But in real life companies confluence is used with hundrets of authors in hundrets of wiki spaces. Even space admins will definitely not be given direct access to the data base with a command line editor. Central Confluence administration can't deal with those many requests for (mass) change.
So those hundrets of authors or space admins need a method to change labels of hundrets of pages in their individual wiki spaces in a quick and comfotable manner. This should not be a funny plug-in, but a core feature of confluence to make it a sustainable authoring tool.
There are so many good controls based on labels. But they can only work fine, if labels fit. And they will only fit if it does not take too much time to adjust them over many pages quickly.
I'm sure confluence will disappear in real business environments as soon as a competitor product has such feature. It is essential for keeping a wiki space alive as circumstances change. Atlassian currently just benefits from the fact, that e.g. SharePoint doesn't have this feature either.
I think this should be worked on seriously not only with confluence admins, but with simple wiki users and space admins, who are responsible for their content on a long term.