I see this is rather old, but I just saw it and it still may be interesting to others.
The way you can do this is with hardlinks. They're more or less filesystem-level shortcuts, so you can have multiple "files" with different names and even different file extensions - all pointing to the same file on the disk.
You can add hardlinks with the program called Link Shell Extension. (Symlinks won't work if the torrent client tries renaming the file).
You also can use the program called DupeGuru to automatically look for duplicates and replace them with hardlinks.
