Change the environment variable name, go through through your apps (and kernel probably) change the code to use a new one. Anything is doable, it just takes time. I'm not saying it is trivial by any means; I'm just saying it is an option. If you build everything from source, it is more doable. In fact, it would be nice to have a secure -nix distro that did it for you. (I know there isn't one that does this, but it could generate a random env var names and paths during install, and maybe change them on demand (by external boot).)

I'm perfectly aware that this could be "extremely difficult" or "not feasible" in many situations, but it wouldn't be so hard to control if you made the device and designed the OS for it (linux-based routers, etc.). I'm just tired of people giving up and laying things out like a holiday dinner because it's "too difficult". Good security requires sacrifice of work and time.