If you were going to do it like this, hard links would make a better option. And in a tag based file system, the actual on-filesystem "filename" isn't as impor

If you were going to do it like this, hard links would make a better option. And in a tag based file system, the actual on-filesystem "filename" isn't as important as the path, er list of tags. This would end up being a maintenance nightmare for different reason, though. You'd end up with two dirs, for example work/projectX and projectX/work, with some files in one and some files in another. Strict hierarchies don't map to tags.