Continuity-wise one thing that bugged me in the Extremis arc was Tony stating that his armor had become too slow and he needed to use the Extremis himself to set up direct neural link with it. Didn't he have something called the Enchapalo link years ago that allowed him to do just that? I believe direct connection to the user's brain was even a major plot point in that was what caused Rhodes to go insane when using the armor that was calibrated for Stark's brain. So after all that, why use Extremis to set up another connection?