well...i think gradings and rankings are juz for 'labeling' sake. I mean,if there wasn't any ranks,you wouldn't know how long that person has been training rite? eg.if i had partnered wif a beginner but doesnt know it cos he doesnt have any thing to show it. He will likely to be injured or hurt.
About the ego, once a person is not ego-istic, he isn't, if he is, he is. These rankings has got nothing to do with it, its all in the person and his willingness to change if he is ego-istic.