Changeable Name Tags

Signs can now be changed after initially editing them; however, name tags seem to be all but forgotten about. To maintain consistency, it would be fantastic if shift-clicking a named mob could open a naming interface similar to a sign. Additionally, there is no real good reason to need an anvil to name a mob if you have a name tag. Name tags are exceedingly rare, so this would prevent the hassle of finding a new one to rename an already named mob.