The file /etc/condor-cron/config.d/condor_ids is autogenerated and overwritten on each update. Users might want to override the setting, which they can do by creating a file (e.g. condor_ids_override) that sorts after condor_ids and sets CONDOR_IDS. (This is already possible, but we need to modify the comment in condor_ids to point that out.)
Also, make condor_ids not a %config file in the RPM, since it's not meant to be modified by the admin.