The closest parallel I can think of is the Gun Microstamping law (which would require that bullet casings be stamped with a mark identifying the gun it was shot with). This has (as you might expect) generated a lot of controversy and lawsuits.
This concept I find interesting. If Apple did have the ability to create this tool, then is there much of a difference?
I guess the difference is whether Apple were to give such a tool to the FBI, rather than creating it, extracting the data and deleting the tool. But who is to say that some clever individual can't create their own tool to achieve the same thing.
Until Apple deliver on their desire to create phones you can't decrypt, I would therefore consider all iphones vulnerable.
And Apple can't decrypt the phone: it can remove the bruteforce counter and/or exponential delay, both of which are paramount parts of the security architecture that requires users to be able to unlock the phone using a 6-digit code (4-digits for non Touch ID phones like that in discussion), which in turn is an important UX compromise to allow to reach the goal of having 90% of 1B iOS devices with passcode lock activated.
Allowing for a remote bruteforce is basically undermining the whole security architecture.
To make a phone that is not bruteforcable, you need to give up on the 6-digit concept, which is already an option (I turned it on on my phone) but it's strongly unlikely to gain widespread acceptance
The FBI hasn't asked for this since they can trivially do it themselves, but Apple could certainly do it if they wanted to.
And if they are forced into creating this hack, then the next request will be to force them to decrypt the phone too since once manufacturers can be coerced into doing anything that the government demands in a warrant, what restriction would prevent the government from asking for full decryption?
Bruteforce protection doesn't mean giving up on a 6 digit passcode, it means making the hardware security module completely hardware only with no way to alter software (or at least unalterable without the unlock code), and with too many brute force tries, the hardware wipes it's copy of the key, which is essentially the same as wiping the disk, but it can't be intercepted by an IOS software change. For added security, it could have a timer so if the phone is not unlocked in X number of days, it wipes its key so if someone steals your phone, it's completely unrecoverable after X days.