There was a jumper on the original phantom that you could use. If you connected the jumper, powered on and powered off, it wiped the memory of the Phantom.
Knowing a little (very little) about software code, those instructions are still somewhere in the code for the P3. Find a mechanical way to trigger that jumper (the main control board of the P3 does not have them) and perhaps you could wipe the Phantom completely, including no fly zone information.
Without a physical hack, software would have to access the memory that stores the NFZ information (it exists somewhere, is writable and unlockable). Forensic hacking would be needed. I'm positive it is do-able, but I won't pay for someone to do it; if DJI is going to force change upon me, even before the FAA, and do so in a more restrictive manner than necesary, I will have no choice but to buy a P2, install lightbridge 1, and go back to a Hero 4.
I just want to take the **** thing up to fly. I'm a pilot. I have a 333. I get the need to promote safety and education, but there isn't an auto manufacturer in the world that limits their vehicles to a top speed of 75 mph.