Problem: Export of Wikibooks to PDF stopped working and this problem is neglected.
Proposed solution: Fixing the broken feature + adding one-click export of the book.
Who would benefit: Anyone with intermittent access to Internet for various reasons (expensive connection, privacy etc.) I myself had an idea to start such a project on Wikibooks, where (a) many people could add their two cents, (b) young readers' privacy is advised so they could download the document and read it offline away from their parents or friends but absence of offline export - prevented me from using Wikibooks.