... just to start a bit of a flame war :), I submit here that a good start to solve the pathname issue is my very own NAMES-AND-PATHS effort.
http://common-lisp.net/project/names-and-paths/
I also have code that implements a lot of the syntax.
Comments and developers welcome.
... and no: symlinks (a UNIX concept and one of the problems that newbies find with ASDF) are explicitely not handled.
Cheers
-- Marco Antoniotti