Currently, I'm mostly working on labeled section transclusion. If you know of any articles that would use transclusions, feel free to leave me a note so I can look at them.
I'd previously developed an initial version of Template:Sec to enable that. The plan was to expand that, mark sections in a few articles, and then replace cut & paste text with section transclusions.
However, the template approach seemed to be intractable for some of the larger cases, so I've reimplemented this technology as an extension, which was activated here on June 22, 2007.
I've updated the scripts I used in the template implementation to start rolling out the feature. This start with some of the articles from Category:Bible_books, continuing what was started with Bible/Obadiah (manual) and Bible/Philemon (via template). Currently, I've switched the assisted editing to sanbeg (bot) (talk • contribs).
Look into splitting footnotes with cite; can use w:Alcibiades as example. See Wikisource:Scriptorium/Archives/2008-01#Footnotes. This is live now; may also add note tag, try to add alternate numbering.
Paradise Lost (1667)/Book I uses line numbering spans inside a poem; maybe html should be moved into the extension.