VCB is ONLY used with NBU if you are using ESX 3.0 and 3.5. Go to ESX 3.5 U2 and vSPhere4, you dont have to use VCB, you can use the vStorage API. VCB support is there for legacy support, as VMware is phasing that out anyways and has no plans to develop it further.
I believe, if you select the physical host in your selection list, or vcenter, it will select all hosts within, even new ones.. This is how it works in BackupExec 2010, dynamic inclusion of new guests.