Thanks for the great feedback! I do really like the idea of offline mode and integrating text-based commentary (there's definitely some great stuff out there). The main hurdle at this point is the licensing fees associated with both these items.
There are roughly 1,900 years of freely-usable commentaries, going by the rule of thumb that anything published in the US before 1923 is in the public domain. (The translations would have had to have been done before that year as well, I guess.) This could be an accessible way to get into e.g. St. Augustine's commentaries.
I think the way YouVersion got around it was having the public domain versions downloadable (so KJV and ASV I think). Maybe that would be enough for now?