I don't know how good of a co-writer I would be because slash isn't really one of my writing or reading preferences but I very much like fantasy/sci-fi and romance and have been wanting to do more less-realistic things if you'd like to go back and forth with some ideas or something, do a two-shot to see how our writing meshes maybe.
I'd be down to explore outside of my box, lets throw some ideas around and see what we can come up with.