Well, it turns out the notion that you can not use a second DC is really just a slight, but VERY common miscommunication from Microsoft. The nut of it is that since SBS 2000 you CAN add additional Domain Controllers with the following two caveats:
- The SBS server MUST have all of the FSMO roles
- You can NOT add another SBS server to the domain… but you CAN add any Windows Server Standard or Enterprise
… It’s just that simple.