If it would be possible to include a few words of warning at the top of file listings, that would be great.
I vaguely remember it was possible to configure Apache in a way that it would include the contents of a README file in the index itself?
Unfortunately I don't think patching Debian-distributed Firefox is going to help much here. The point is that these files need to be downloadable from a non-Debian OS!
Did we try talking to the problematic mirror providers about the issues our users are facing? I understand this may be a delicate issue to some, but I guess it does not hurt to at least start a discussion?
FWIW I don't think Google's file scanner cares whether the mirror is in Sweden or not :-)