I agree with the PP's -- although I prefer Scarlett Elizabeth, nn Scout -- I know a young Scout and it just doesn't seem like enough of a name to grow into. President Scout ____? or Grandma Scout? As a nickname, it's adorable; as a full name, it seems a little lacking.
But unlike princeotto, I'm a fan of a big grown-up name with a day-to-day kid-years nickname. So opinions will obviously vary!! :)