Fanfiction stories are easy to write because you're using established characters, in an established universe...
I've no doubt there are many people who would be interested in seeing that type of fanfic though.
Very true!
BTW -- There are lots of HP fanfics --
http://www.fanfiction.net/c2l/224/0/1/ -- and I have seen a couple of HP fanfics regarding BE and FMG. One had Hermione and Ginny magically "helping" each other in order to better attract Ron and Harry, respectively. If I recall that particular fanfic correctly, the two girls ended up becoming more attracted to each another than they were to the guys.
Tschuss!
Hunter