well, there is no choice here … you get all of them or none 
the only permitted syntax for using hardware-observe is the one i gave above … replace read-proc-cpuinfo in your plugs: section with hardware-observe and remove the read-proc-cpuinfo block at the top …
also, when pasting yaml, use three backticks ``` above and below your paste, then the indentation persists and the file stays readable …