Is this possible with 2.4.21, or do I need to stick with an older version of OpenLDAP?
Modifying the core LDAP schema is ill advised and should be avoided. I'm guessing you're getting a sane response from trying to do something insane.
--Quanah -- Quanah Gibson-Mount Sr. Member of Technical Staff Zimbra, Inc A Division of VMware, Inc. -------------------- Zimbra :: the leader in open source messaging and collaboration