What if the defense decided to make their own adjustments?

It seems to me that our defense is in the same formation 90% of the time. We hardly see a linebacker or a cornerback fake a blitz or even move around the line of scrimmage. Do you think that Schwartz tells them not to? If so, then what would happen if Bulluck faked a blitz on his own? I mean, these are professional football players, they're smart enough to make they're own reads on the field. Is Schwartz preventing his defense from excelling?