it's not a terrible idea, but my understanding is that the download bandwidth on dc is really not a problem, so it would really be a matter of solving a problem that doesn't exist, while adding a lot of extra coding.. it's not a bad idea in general though, and it could be something to think about for some software if dcupdate is to become more general.
for example the remote update file on the server might simply point dcupdater to a torrent or file checksum which dcupdater could then launch in an external tool. so dcupdate would detect a new version, alert user, and then initiate a download of the new version via an established torrent tool.