I am in favour of this.
We have several boards here that see barely, if any, use, and yet they're allowed to stay. ("Book Fanfiction", "Comic Fanfiction", "Full Metal Panic Fanfiction", "Super Robot Taisen Fanfiction", "Bleach Lemon Fanfiction").
Original Fiction is fiction still, and, to be honest, it takes a whole lot more to write Original Fiction than to write fanfiction of any anime/manga/omgtentacles hentai fanfiction.
Why? Because one doesn't have the basics and the framework laid out before him/her/it, and thus must work hard(er) to achieve this.
Original fanfiction is, to be honest, a great way to relieve one's mind of stress and to flex the brain muscles... and, to be honest, to get rid of Writer's Block, since, for once, you don't have to worry about staying in character, since the characters are your own.
As it is also a good test to see how OCs would play out (since one can flesh out the OC without the constraints of canon, and then see what fitting him into canon would result in - destruction of the OC because he doesn't fit into the canon world or a workable structure.)
Many words say just one thing: I am all for it.