I don't agree that it should be fully automated by any stretch of the
imagination. I can see that it is an option that some may wish to use, but
I dislike the limitations, and do not see it working as the only means to
use.
Well, I think that the bot/Lua/extension/whatever could show to the user a window with the structure of the book as it would be created.
The user could change some things, or Cancel the automatic transclusion.
I don't know: to me, avoiding the burden of taking care of different namesapces, with diffirent templates needed and strange tags (eg pagelist)
should be an aim for us, if we want the layman to understand Wikisource and contribute.
I myself can't upload and create a whole book from the scan to the ns0 transclusion without mistakes or forgetting important things.