It might be a handy upgrade to the field, but… Elliot relies on existing functionality in many places. In this case he’s taking advantage of a popup that already exists and just storing the information that it returns. The link field is designed to work with any link, meaning it can be linked to something other than a post and in this case a post ID would not exist. To do this a new popup would need to be created at the minimum, different information would need to be stored like is it a post/term? Does it have an ID? if it does store the ID and if not then store the URL, format the return value differently based on this. More than likely this would mean a completely new field type that does everything that we can using a combination of several fields.
