I think an awesome feature for FDM would be being able to share files without having to upload them to somewhere else.
Let's say I want to share a movie with a friend and I have that movie on my computer. I'd select that file (or drag it to FDM) and FDM would show/present me with a code, after that I'd send that code to my friend, then when he uses that code in his FDM, it would start to seed my friend's download from the file I have in my PC,