How about this?

Package GetoptReplacer;
sub foo { }
sub bar { }
our $baz;

# magic!
my %g = %Getopt::;
%Getopt:: = %GetoptReplacer::;
our $AUTOLOAD;
sub AUTOLOAD {
  goto &$g{$AUTOLOAD};
}

# less magic
1;
[download]

I don't know if this will catch fire, but there it is.