Spun out of T170687:

It would be useful on many of the pages listed above in T170687#3439746

E.g.
Special:ShortPages and Special:DeadendPages could then be used with the Help: and Project: namespace to find things to cleanup or merge
Special:LongPages could then be used with the usertalk namespace to find people to nag to archive their overwhelming talkpages.
Special:AncientPages could then be used with the Help: and Mediawiki: namespace to find things to update or reconsider the defaults.

Note: Special:Random already has this functionality, similar to solution (f) but using full namespace names, per mw:Help:Random_page e.g. full list at https://en.wikipedia.org/wiki/Wikipedia:Random

Unknowns

• Some design for how the filters should look. Tabs? A search form? A drop down? Is this covered in the UI standards spec?
• More input