Hmm I think it'll still bring in the issues also brought up by others: that if there's a whole section it might encourage more to post it here and then have a hard time transitioning to original works. I've seen it on other sites that offers both and audiences built on fanfic is really hard to get to read anything but the fanfic you write/create. And then they'll go back to posting fanfic because that's what their audience want. Or others will see the numbers and write fanfic because "it will get you noticed."
All this is purely based on experiences from other sites, and it might not happen here. But I'm wary of it because it can create a bad circle for creators who're trying to make their own original work, see very little traffic on it compared to their fanfic and then lose hope for ever creating their own thing.
I think Tapas is fostering a community now that is motivating people to try out original works. And I think it's really special because so far I haven't found any other sites who'll do it as much as Tapas does. There's so many sites for fanfic - it'd be nice if there was one that wasn't.