Are there any known issues/caveats with having /var/adm/CSCOpx as a soft or hard link pointing to another file system? I vaguely recall going through heaps of trouble with this in LMS 2.2 or 2.6, particularly with patches.
Yes. This should be an actual directory. If it is a symlink, you run the risk of having the symlink overwritten with a physical directory after each update. The fix is easy (just remove the directory and recreate your link), but it can lead to confusion.