I liek the idea of growing Heyuri's fujoshi demographic, though I'm also not sure how much activity a dedicated board would get. There are existing websites that cater to fujos, but I dunno if they allow shota or some of the other "acquired tastes" that Heyuri allows

If we do happen to have a sizable fujo demographic already, my guess is that they hold back from posting BL on Heyuri since they don't want to draw ire from the non-fujo users. I don't think they should worry about that since any otaku interests are welcomed and protected on Heyuri, but I can understand the viewpoint - I personally have found myself holding back from posting otokonoko material since I know it's not for everyone and I don't want to be annoying