Could that 'physical' write-protection be bypassed with a 'secret' instruction code? By the way, my comments have only been about the 'code' cartridge, not the tally cartridge. Also, are you aware of 'microcode'? Much can be accomplished with it you know. I've spent 1 career in electronics, another in software development. I am very aware of what can be accomplished with our amazing technology.
If public trust is ever desired and accomplished then methods and procedures the public can easily understand must be utilized. If public trust is NOT desired then, by all means, use technology that most people do not understand. It isn't easy to be aware of what electrons are doing. They're very small you know.
You want “write protection”? Don’t use a re-writable programable ROM chip. Write once. The media couldn’t HANDLE any attempt to change it. There would be no “override”.
How do you propose to write to a parallel flash memory chip without physical access to the /WE and /OE pins (the former pin being pulled high and the latter pin both pulled low and strapped low by the cap)? Is there any reason to expect any off-the-shelf flash chip to include such a feature?