I absolutely understand that, but what I was alluding to was that it would be nice if we didn't need the metafield id in order to perform an update. Because the metafield id is required, I either need to store the ids (I am updating multiple metafields at the same time) in hidden form fields and somehow associate those with the meta form fields so we can update the correct metafields on save, or perform a GET prior to the update/PUT to retrieve the appropriate IDs. If I were instead able to send a namespace and key in place if the id, it would definitely be preferred. It would be nice then if the API would be able to determine whether to perform the insert or update based on the existence of the namespace/key.
P.S. Thank you for taking the time to respond.