I would do the following:
- Keep the Tablo as the DVR.
- Either wait for the ATV App, or offload to Plex for viewing via (Tablo Ripper for Windows/ SurLaTablo for others)
- Use something such as HDHomeRun Connect for Live
This is almost the same as what I am doing on my Shield/ Nexus Player setup. (The difference is that I use the actual Tablo app to view RECORDED shows, and my Plex Library is focused on my purchased media)