As well as telling Mikimi to put the real notebook in the safe deposit box and send Takada the five pages there was one thing Light should have added that would have allowed him to win. If he had told Mikimi to also take out a sixth page and keep it away from the real notebook, maybe at home in a place only he would think to look in. Then given him orders to no matter what happens not to touch that page before the day.
That way Near would have thought he had modifed the real notebook and everything was safe when however Mikimi would have a real page to use on the day.
In saying this I do still believe that Light was a villain, just sayig that there was away he could have won that I thought would have been easy for him to think of.