Actually, I think a path to point to the specific configuration file you're adding is better.  The problem with adding a configdir element to koha-conf.xml is that it doesn't distinguish between configuration files that are shared by all Koha sites on a server and which are not.

For example, on a Git install you can assume that all Zebra configuration files live under $configdir/zebradb/, but the Debian package puts some in a shared /etc/koha/zebradb/ directory and some site-specific ones (e.g., zebra-biblios.cfg) under /etc/koha/sites/$SITE.