The urge to tear down the stack of cellphones I have and pull the boot flash chip hits me occasionally. It would be a substantial project, though, so I haven't done it. Yet.
how far down the chain does the protection go? if you swap the flash chips can you just boot or do the other chips expect a signature upstream?
You have to do things. You can't sit on project ideas forever while they become obsolete. A lot of things on my project ideas file became obsolete while I didn't do them, and that is sad. I even had enough time to do them but still wasted it on places like HN.