This seems to be just the project for me. I have experience working with Raspberry Pi-based audio-video applications as well as terminal user interfaces. In the past I've made digital signage that looped through lists of images and other digital signage that shuffled through audio and videos on removable storage. Only point of concern is the specifics of the interfaces, biggest question being "what's on the other end of the USB cord?"
If you have no preference on the tools used for this, I could provide you with a statically-linked binary, sources for it, and a simple config file to launch the service on device boot. Hope to hear back soon and hope to be working with you!