Sorry for the double-post.
...alright, I tried to do a little bit of research (or more like Googling around.) I cannot fully understand it, but I think I found a little excerpt of
Hinamizawa Bus Stop in a blog entry by 07 back in 2003.
A conversation between Rika and Mion.
Rika originally being an older girl with Mion as her junior sounds about right... (correct me if I'm wrong.)
EDIT:
And got confirmation from a friend- yes, this is the original script.