to clarify : the 2nd button would operate exactly as the current 1st button does, fuel etc shutoff no questions ifs or buts. It could be operated without button 1 having being operated, but that would be outside SOP, but would be available for cases where button 1 (joint control by pilot and computer) doesn't shut the engine down.
What I'm aiming for is the mental break, almost a 3rd pilot in the cockpit saying "wait a minute".. By making the pilot move towards button 2, when button 1 should have done the job (Jeju, Kegworth, AI) it means the computer thinks its not a wise move, and it will hopefully make the pilot take another few seconds to say "weird, why does the computer not like my first command" and perhaps another instrument scan and check.
99.99% of the time in line operations button 1 is the right button to press, so when a pilot is directed to button 2 they should take a second to re-evaluate. It's a trade off. It's an extra 5 seconds in worse case emergency, say engine fire and computer US, but in many many routine ops that have a minor emergency it will actually prevent a crash.
Simon