He has done a remarkable job for Mumbai Indians whenever he has batted there barring the last season. When Rohit began opening the batting, it was said he in not suited in that position and was strictly a middle order batsman.
Personal batting positions and numbers are more embedded in fans and followers and not so much the players. They do what is right for the team and at the moment, India can do with his experience in the middle with Dhoni leaving. Rohit is so good that he can tonk it around from ball 1, something even Kohli can't. Dhawan has to open and it is criminal to leave Rahul out any longer in the format. Off the current lot of batters, Rohit is the only one who can basically bat in any situation and the prime reason for that is the time he has to play shots and the range he has.