Suggestion: User > Editor able to alter navigation menu

I've noticed that if you add someone as an 'Editor' that they can add and delete pages, however they are unable to add these pages to (or remove existing ones from) the navigation menu.

Is it possible to add this or have another type of user who has that ability - such as 'Supervisor' or suchlike?

My reason for asking is that a client may need full control over the structure of the navigation of the site but you don't want them to mess up the theme files etc.