You would need to modify the execve system call (or equivalent non-Linux OS's) to take in the 4th json arg for the shell to pass when it exec's the new process. And then of course modify the OS kernel to parse/deal with it. But in reality, since you can't break the ABI like that for all existing software, it would end up being execve_2 or something and you'd have to both convince everyone else it's worth using, and deal with the inevitable incompatibilities when not everyone does. Not impossible perhaps, but certainly an uphill battle.