u need only to set the launcher for don't download update if it need more than XX mb ...
if is more redirect to other sources (direct download/torrent) they are faster too ^^
and btw if i remember well the wow updater was with a bit torrent client (i don't remember what game was :P)
btw if u wanna do a cool thing u can implement a torrent client inside the launcher and u solved all the problems :P