Mmm... that would work on the whole, but it feels a little clunky and awkward. Besides, it doesn't work with symlinks in the way I'd want it to:
Let's further assume that /foo/bar/share is a symlink to /usr/share. Then if we're in directory /foo/bar/bin, I want "../share" to be expanded into "/foo/bar/share". However, CDing into the argument and issuing pwd would return "/usr/share".
The command I had in mind, IIRC, essentially performed variable substitution on the supplied string, such that "~" at the start was transformed into the absolute path of your home directory, etc. I could write something similar myself as a short shell script, but distributing shell scripts isn't an option for me - I need something that'll run in /bin/sh on most *Nixes.