Submitting IDs : yes ..
Trying to think how to explain this properly. If you look at existing form fields you see all the flexible fields go under ```values``` in the post json. Each of these is associated with both a post id and form attribute id. Ideally media should be the same (not just associated with a post).. and potentially support multiple media fields create in the form.
Does I make any sense? .. if not I'd better start drawing diagrams or something :)