If Emby used or easily supported using Ripbot264 instead of ffmpeg you could use Ripbot264's distributed encoding feature. https://forum.videohelp.com/threads/386325-Ripbot264-Distributed-Encoding-Guide    You can do it currently if you are just wanting to use it to transcode recorded TV or batch convert something before it is requested.  Using the "LiveTV" post recording processing option to specify a script file that calls Ripbot264 to do the cluster encoding you could leverage it that way.