go get bitbucket.org/ronb/mlml is a very simple tool that combines ln -s and mv:
$ touch from
$ ml from to
$ ls -la
total 8
drwxr-xr-x 2 r staff 136 Jul 29 20:53 .
drwxr-xr-x 4 r staff 306 Jul 29 20:52 ..
lrwxr-xr-x 1 r staff 2 Jul 29 20:53 from -> to
-rw-r--r-- 1 r staff 0 Jul 29 20:53 to
$ ml -reverse from
to