Recent releases have added changes to make seamless networking work. As a result, setup of more complicated services such as ldap have become more difficult. For example, on 8.04, knetworkmanager likes to bring up the Ethernet connection after the user logs in, thus causing issues with LDAP which needs to connect to the LDAP server before the user logs in.
I had a similar idea a few days ago I just submitted. I feel the best approach is adding plugin support to Network-manager. This way we can improve it, and change its behaviors as we wish!