Hello everyone!
I have just finished my initial version of a dockerized configuration that implements two containers: the standard plex container, and one that I create (called plexpost). It is set up as a docker-compose service pair. When configured properly, after the DVR completes a recording, the post-processing script will add a queue entry to the post-processor which will then either do commercial marking (using comskip) or commercial cutting, and then transcode the resulting file to h.264 in an mkv file. The resulting file will replace the original .ts recording in the plex media library.
If you want to try it out, it is freely available on my github page: https://github.com/mjbrowns/plexpost
Please enjoy and comment! Bugs and enhancement requests should be left on the github page.