I have some limited experience using PHP XML functions and IMHO once over the initial learning curve it’s fairly smooth sailing. (dealing with namespaces being an exception).
I think what would be the biggest hurdle for me would be putting together a recursive interator with the correct logic.
I’m also thinking that for something as large as the Bible there’s a better than good chance there will be memory and timeout issues. So breaking things down to “per book” would likely be a good idea even if it wouldn’t be a necessity.
In fact, I’m certain that during develop I would limit the work to a smaller subset of data instead of trying to work with it in it’s entirety. And then, after I was sure everything worked, then, maybe, I would try having it work with larger data sets.
I’m also wondering if XML is a better choice than database tables.