This idea has been talked about a lot lately after the ruling on the killing off of the CableCARD about a month ago.
My idea is to have Channels coordinate and manage all the content streams (TVE, OTA, and CableCARD while it lasts) and then present itself to Plex as a regular TV Tuner on the network. (e.g. HDHR tuner)
In my case a remote TV Headed server would be ideal because I have Frontier FiOS where I live and they don’t offer TV in that location anymore. But my apartment where my Channels DVR is has Spectrum where I subscribe to TV and internet. So if my Plex server could talk to my Channels server it would be a seamless solution.