I would either go with number 1 or 3. 1 being I'm a fan of 1D (obviously ) while 3 is an original slash. I'm not exactly a slash fan, but once in a while, I don't mind giving it a go. I didn't read The Hunger Games Trilogy, so I'm not able to relate with the second story (or anything to do with THG).
But I would seriously vote the third one. 1D romances are... Well... A bit too much going around Mibba already... Unless there's somekind of weird twist in it.
I'd read The Hanging Tree - simply because ever since I first read the books, the song's and it's story has been stuck in my head. I'd love to see it play out as a stand alone story (I also can't wait to see how it'll be portrayed in the movie).
I think I'd read all of them actually, but I would definitely read #3, just cause I haven't read a slash it quite a while. If I find my old one, I will definitely need to post it up.
But I would seriously vote the third one. 1D romances are... Well... A bit too much going around Mibba already... Unless there's somekind of weird twist in it.