Signaling and Information

One basic concept which has emerged in classical physics (and then moved on to the quantum world) is that it doesn’t appear possible to send information faster than the speed of light. What I find fascinating about this is that it seems to be, like Landaur’s principle, a statement which connects physics (special relativity, local field theory, quantum field theory, etc.) with, essentially, information theory (the concept of a signal, the concept of information capacity).
But now suppose, as I have argued before, that what makes a physical system a “storage” device is very much a matter of the physics of the device. Thus, for instance, I could try to encode information into the position of a particle on a line. Is this a good way to encode information? Well, certainly we could try to do this, but in the real world it will be very hard to achieve many orders of magnitude precision on this measurement because the system will interact with the rest of the world. While isolated we can talk about such an encoding, but as we crank up the real world meter, we find that there are limits on this encoding. Or to put it another way, the ability of the system to store information is a function of how it interacts with the rest of the world, a function of the physics of the system.
And if the ability of a system to store information is a function of the physics of the system, why isn’t the no-faster-than-light rule, a rule which is essentially about information transmission in physical systems, also a function of the physics of the system?