Well, you may be incredulous, but I already do it with a script.  HTT knows
where it would put the file if it were part of the mirror, so all it has to do
is make the link point to that place.  Then if ever I do in fact download that
page, the link will be correct.

It would help me break down big downloads into smaller parts, which have a
better chance to succeed - as you can read in my other post, I may have lost
over 75GB worth of mirror, and it would have been a lot less painful if I had
been able to download that, say, 10GB at a time, thus capping the maximum loss
of a glitch.