At first glance, this looks like some functionality that is on the general roadmap. I think the biggest challenge is coming up with specifications that are coherent with what already exists and reasonable for tools across the ecosystem to support.
What's higher priority, this or Collect will need to stop using /sdcard/odk for files - #23 by Kigamba? Could y'all maybe free up some cycles to think through this by doing pyxform/XLSForm review?