That picture has me cackling, for whatever reason.
It seems unlikely that Britney would ever go that short, and I don't think it's a good idea for her right now, but I would sorta love it as some desperate "reinvention" moment in a few years.
She needs long blonde hair. And, in a perfect world, some weight loss (just a healthy amount, I don't want her anorexic). And plenty of sleep. And spunk!