On FAT I don't think you have any options like this.

Right. While it is possible to create a hardlink within a FAT filesystem using a disk editor, most -- if not all -- FAT filesystem checkers consider this a filesystem error. FAT is defined in a way that each file must have exactly one directory entry, and so the fully qualified file name (relative to the filesystem) uniquely identifies a file. With VFAT (i.e. FAT + long names), things become a little bit different, because each path element may have a "long" and a "short" name. Normalizing the paths of two files to use only "short" or "long" elements gives compareable, unique identifiers.

Alexander