Usernames, I treat them like real names, and have nothing to do with appearance.
No, I won't need to do that, it's very easy to imagine the face as a group of shapes already.See how it works if you draw someone from a reference, but do it with the face upside-down. It's a trick my drawing teacher from a couple years ago taught me; apparently it makes it easier to view the face as just a 'group of shapes'.
It's just that very minor changes can be exaggerated.
Here's why your method won't work too well:
http://www.exploratorium.edu/exhibits/mona/mona.html