If they are networked together I believe you can only add the one account via ldap to the one unity connection server per user. You could create a new user without a mailbox then assign them roles accordingly but it would not be ldap authenticated.
But we can break it down real simply,
if you have a single site either a single voice mail or admin user/ non voicemail account you just assign roles and that is it but that user first has to exist. So options are local user account or ldap sync last imported user.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.