When creating a post or uploading to the media endpoint the spec currently only requires to return a location header.

This is all fine and well if you are creating a server side app. But if you are creating a JavaScript based client at least it can be very difficult, if not impossible to read headers. All that is needed to make js clients more viable would be to return the location either in the body as plain text or a JSON object (would make more sense in case more values are required in the future).

I think this is especially relevant for media endpoints as one of the primary purposes of media endpoints is to enable rich editors which can only really be achieved on the web with JavaScript.

Having written this now however I realise it is all potentially a moot point unless micropub endpoints are set to allow cross origin requests. But still something worth considering.