I don't know if I can't find the option or if it has been removed, but I seem to remember many versions ago there being an option that if the podcast episode was no longer on the RSS feed, it was auto deleted.

I mainly use my cell phone to play episodes and I manually keep my cell phone in sync w/ the RSS reader I use (Bazqux), but allows me to to share folders of podcasts/rss feeds out as a single feed and I can further add to the RSS feed to only show episodes that are marked as unread.

Periodically I listen to episodes on other devices such as my tablet. What I would like is to make it where when an episode on Bazqux is marked as read, it will disappear from the RSS feed, and be deleted from my tablet.