The 49ers were a team built on good chemistry. Bringing Moss in will only disrupt that chemistry.
I believe that where you went wrong was in thinking that Harbaugh would allow one player to disrupt the team chemistry...
I think Moss is over the hill, and will be retired again by week 6.
This would not surprise me at all.
Bottom line...no one knows what sort of attitude Moss will bring to the table. According to the folks who have seen him during his workouts with the Saints and Niners though, his physical ability to do the job is just fine.
In the wise words of Dr. Seuss: "we shall see, we shall see..."