You can either complain about Error 53 if someone-not-Apple replaces part of the Secure Enclave of your iPhone, or you can complain about the FBI having a backdoor into your iPhone (and by extension, the Russian Mafia – because if the FBI can do it, so can anyone else of moderate technical skills. The FBI are a bunch of hacks).
But you can’t have both a secure phone, and allow third parties to change out fingerprint sensors.
In this case, the FBI is asking for a court order for a Silicon Valley company to write a special one-off version of the OS that will allow hacking. Imagine what happens if that succeeds. Every company in the US will be subject to court orders to rewrite their OS to allow the government to do something.
The end result of that, I think, would be for software operations to move off-shore. Goodbye, Silicon Valley.
Or, as Apple has tried to do, with the hacker community up-in-arms about no-right-to-repair iPhones, install a Secure Enclave of encrypted parts that not even the manufacturer can undo. In fact, if you get a repair with a manufacturer-unsigned part (third party), as the FBI (or the FSB – pick your TLA, not all of them are friendly) might try, the phone bricks.
Even the manufacturer can’t repair the part without wiping the phone. Hope you’ve got a backup.