Discuss the merits and demerit

The advantage is that there is greater transparency in the sense that the user does not need to be aware of mount points and create links in all scenarios. The disadvantage however is that the filesystem containing the link might be mounted while the filesystem containing the target file might not be, and therefore one cannot provide transparent access to the file in such a scenario; the error condition would expose to the user that a link is a dead link and that the link does indeed cross filesystem boundaries.