It'd be difficult to convert hard links to symlinks. In the case of a hard link, there is a data block on the filesystem which has two or more file entries pointing at it. There is no "source" and "destination"; it's literally one file with multiple equivalent names. You can use GNU find to identify those this way:
sauer@zipper:~$ find . -type f -links +1 -printf "%i: %p (%n)\n"
609: ./link1 (2)
609: ./link2 (2)
Once you've got all of the files with the same inode, you'd have to pick one to be the "real" file and then just replace all of the others with symlinks to the master file. Probably the way to do that would be to use this:
sauer@zipper:~$ find . -type f -links +1 -printf "%i %p\n" | sort -nk1
And then have a script figure out how to pick one of the values with the same number to have all the others link to it. Maybe the first one becomes the target, and any more with the same inode are symlinked to it. Here's one really simple, untested shell script example
find /tmp -type f -links +1 -printf "%i %p\n" | sort -nk1 \
| while read inode file
if [[ $inode != $prev ]]
ln -sf "$target" "$file"
There are potential problems, in that links from different directories may be created with an invalid target if the path in find (/tmp in this example) is not absolute. But the general idea should be fine.