I'm a developer at DPLA and so happy to see some of these comments. We are obviously a small org (and even smaller tech staff of three) and it means a lot to me.
Thank you for this, I have huge respect for the ideas here.
I use Libby to access public libraries. Have you considered giving Libby/Overdrive access to your items?
DPLA is a strategic partner with Lyrasis on a platform called The Palace Project which is an alternative for public libraries and includes a marketplace for acquiring content to lend, circulation management as well as a patron facing app.