I've got it working with a node script to change the id3 tag, and re-add to itunes, that triggers a smart playlist called "Watch Podcasts" in the Music section.

Then the node script triggers AppleScript to Update iCloud Library.

The "Watch Podcasts" smart playlist is added in iPhone Watch app under Music.

Now when the watch is charging any of those podcasts are synced.

Don't have a clean way to share (and selecting podcasts to transfer is manual on the Mac).

If there's interest I may expand on utility and share