I like Mark Cook's idea of equating level X skill with something
identifiable. It would be interesting to compile an exhaustive list
(if such a thing could exist). The one I always used was:
Medical:
level 0: know when to call a doctor
level 1: a good thorough, working knowledge of first aid
level 2: equivalent to emergency medical technician or nurse
level 3: equivalent to an intern
level 4: doctor (U.S. type) or surgeon
level 5: highly skilled neurosurgeon
level 6: breaking new ground in medicine
level 7: Hippocrates :-)
The caveat about U.S. type of doctors is because I don't know much
about any other type. It could be quite different. Level 4
witch-doctoring or shamanism might be quite useful.
Richard Johnson