Release a Garmin App
Most podcast apps are awful and make syncing podcast episodes, marking them as played and removing old ones either very difficult or impossible. You have nailed it on android.
Now I need the same on my Garmin watch. There are currently only 3 podcast providers for my Garmin 645 Music watch and they are all unusable. This could be a great market to tap and would make your Garmin owning fans very happy.