the problem with that is the hdd. the scan from black ops 2 scans the hdd itself. since the hdd has read/write access, it's the easiest way to know if someone is on cfw. that's why it's recommended you have two hdds, one for cfw and one for ofw, if using a true dual-boot. using an hdd from cfw with ofw would have no effect on these scans due to this. also, swapping drives is impossible. the hdd serial number is recorded in the xregistry. if the system detects the wrong serial number, it will attempt to format the drive. the xregistry, at least with NOR consoles, is on the hdd, so you could swap drives if using a dual-boot without issue.
there are too many issues to do what you're asking. there was an app to load firmware from usb, but that would have no effect on the hdd. I think that's why the black ops 2 scan was designed this way. as you know, the ps3 can't run without an hdd. that's why the ps3 has data installs and the 360 doesn't. to do what you ask, may require all keys, but there are a lot of unknown ones.