Now that #1801304: Add Entity reference field is in and #916388: Convert menu links into entities is Rtbc I think we should be giving consideration to using an entity reference field to replace the menu module's node form additions. We have issues to convert path #1751210: Convert URL alias form element into a field and field widget and comment #731724: Decouple comment.module from node to field API. This would
*let us have menu integration for more than node entities
*Let us keep track of multiple menu links for one node
*Remove code that looks up link path in the menu links table in order to find an association and instead use a first class reference
*Unify the way to add form elements to an entity form, less form alter, more field API
With the entity reference field slated to replace taxonomy reference there already has to be logic to auto create taxonomy terms, it could be extended to auto create menu links for this instance and would be utilised on the node form when adding a new link