Hm, it was so long since I read that prologue - but I remember that I was slightly confused over the format and thought it was a bit dragged out*. (it was my first VN)
So I wasn't terribly disappointed at the switch as the cast quite soon started to fill up with interesting characters, including Rin.

But I wont deny that it would been interesting with a female protagonist for a change, and then Rin wouldn't have been a bad choice. (although you would lose one great supporter character)
The story would have been radically different though.

*Partially due to me not finding the save-button. It turned into a late night.