I agree with this, so long as the bans, kicks, whitelists and things of that nature do, as you said, use the person's username. However, I feel that this will probably happen anyways a little while on but it's probably the type of thing that would require a pretty big amount of code change. I don't know anything about Java, though, I just say that because of the way the player authentication system is currently set up.
My life is all about punching trees, mining, crafting, building, punching spiders, fighting zombies, running from creepers, respawning, finding back my shelter and punching more trees. Yup, I wish I actually had a life.