What you actually want is a NAND emulator on an FGPA. Then rolling back the NAND to a eariler state is simple and can be done in a split-second, much less than

What you actually want is a NAND emulator on an FGPA. Then rolling back the NAND to a eariler state is simple and can be done in a split-second, much less than the actual time of the reboot. Depending on the software-implemntation, it might even be possible to roll the NAND back while the phone is still on, saving you the reboot. So your time is bounded by how often you can reboot. However, I'd be highly supicous that Apple might have a few bits of perminate storage inside the SOC and can detect multiple re-tries even without trusting the NAND.