Do you want such a tool (the one the removes the security of updating) to exist so that anyone with physical access can replace the OS with something else?
I don't understand what you're getting at with the "tool" question. Nobody's talking about building something that lets anyone with physical access replace the OS. The phone's secure boot system will still require updates to be signed by Apple. Apple can replace the OS with physical access. On older hardware, it seems they can do this without wiping the data. Do I want Apple to be able to do this? It doesn't matter what I want, the fact is that they can. Since they can, and since the FBI has a court order, I don't see what's wrong with requiring them to do so. If you don't want them doing this to your phone, buy a newer one with the more secure hardware.