The part of the identity retention, I just see that as Lucas trying to give the character some justification for having such a large part early on in the series. Originally, it wasn't going to be explained, something that Old Obi-wan had up his sleeve, but once again, the old reliable has been stripped of his dignity. Not only is Obi-wan a liar and a thief, but he also can't figure things out on his own. Even then, it was also said that it was taught to him by Yoda, something he knew that he passed on to his student. That would have strengthened the bond between master and student, but since Obi-wan was one of thousands to be "instructed" by Yoda, it dimishes the strong bond we were being led to assume with the OT.