OAM and OID is really required.
It is coded in the EBS code.
you can still do the same by developing some customized applications, but this will not be supported.
Bytheway, this seems to be a duplicate issue ->
http://erman-arslan-s-oracle-forum.2340467.n4.nabble.com/OAM-OID-integration-with-r12-2-td7662.html