I've just started using HTTrack and I'm very impressed. 

Would be a possible to add a new option to HTTrack to prevent it from
downloading a file if it already exists on the filesystem, regardless of
whether a new version of the file is available on the website?
Obviously this option would be turned off by default, but it would be very
useful when you have a local copy of a website where the timestamps on files
are messed up, and you don't want HTTrack to download everything again.