There is no reason why you cannot do that. As long as your definition of "identity" includes the interface IP addresses as well.
However, I think the more efficient way to do this has been documented at CCO:
http://www.cisco.com/en/US/products/hw/vpndevc/ps2284/products_tech_note09186a0080094490.shtml#synch
Here you do not have to use the CLI nor do you have to isolate the Backup. You just have to make sure that you disable VRRP before writing the configuration onto the Backup device. Alternatively, you will not even have to disable the VRRP if you can determine the parameters which you have to change in order to reflect the device as a Backup, in the CONFIG file from the Master.