First and most important of all.
If you're dlding a movie and the user goes offline, you can do a search for alternate, but when you start dlding the same file from another user, it starts back from scratch, it should resume where it stopped.
Second.
You should be able to dld one file from multiple users like kazaa so it goes even faster. I have a very fast connection (fiber) and i never get the max out of it if i can only dld a file from one user
If these features are already proposed, i apologise...