Apple also has a huge firewall (in the figurative sense) right now in that it is a large amount of effort for them to create this new security-relaxed version of the OS, and the government can't be compelled to force them to produce it.
Now, let's say that they have written it for some reason, but it is restricted to a single device id. Well, it's now a lot easier for the government to compel Apple to hack another phone, because they can creditably argue that all Apple has to do is change some string constant and re-sign the package. The burden of work is now much, much less than if the tool itself doesn't already exist.
Apple doesn't want to ever create the tool. If they have to create it for any reason, even if it starts out being locked to a single device id, they've lost the war.
Now, let's say that they have written it for some reason, but it is restricted to a single device id. Well, it's now a lot easier for the government to compel Apple to hack another phone, because they can creditably argue that all Apple has to do is change some string constant and re-sign the package. The burden of work is now much, much less than if the tool itself doesn't already exist.
Apple doesn't want to ever create the tool. If they have to create it for any reason, even if it starts out being locked to a single device id, they've lost the war.