Here is port of DragnoFly BSD's variant symlinks to FreeBSD CURRENT.
(http://freebsd.org/projects/ideas/#p-magicsymlinks)

Variant symlinks is a dinamyc symbolic links. Source file of a variant 
symlink may contain one or more variable names. Each of these variable 
names is enclosed in braces and preceded by a dollar sign in the style 
of variable references in sh(1). Whenever a variant symlink is followed, 
each variable found in source file is replaced by its associated value. 
In this manner, a variant symlink may resolve to different paths based 
on context. 

Installation instruction:
1. You should have freebsd source tree.
2. 
	# cd /path/to/src/parent/dir (default is /usr)
	# patch < /path/to/varsym.YYYYMMDD.diff
3.
	# cd /path/to/src/sys/compat/freebsd32/ && make sysent
	# cd /path/to/src/sys/kern && make sysent
4.
	# cd /path/to/src/
	# make buildworld buildkernel
5.	If no errors - installkernel and installworld (see handbook for details)

After upgrade world and kernel you can enable variant symlink via sysctl
vfs.varsym_enable.