In over 5,000 hours flying the 777 I never found the need to de-power an entire AC bus in order to take 'direct pilot control of the aircraft without interference from the FMS'.
And presumably you've never had the need to turn off the transponder either, yet these are things that happened aboard MH-370 that night.
We have to address the facts as they present themselves. One fact that won't go away is that there was a satellite communications blackout from 9M-MRO which began at 17:07:48.9 and lasted until 18:25:27.4 when the sat modem initiated a cold login to the satellite. A cold login would only be caused by restoration of power unless you prefer to think that this sat modem which had performed flawlessly since the plane was delivered from Boeing, all at once developed a bug the same night the plane was diverted to the southern ocean.
The sat receiver/transmitter/modem receives its power from the left AC Bus in the EE Bay. Down there there are three circuit breakers which provide the only way to turn power off to the sat equipment. There is no way to power off the sat equipment from the flight deck other than to bring the left AC Bus down. Your "
on the 777s I flew there was definitely another way of disabling the system from the flight deck" reeks of the kind of stuff that comes out of the Malaysian transport/defense ministry. It appears that you parsed your words to give yourself as many outs as possible.
Let me state it clearly: there is no way to remove power from the satellite modem/transmitter from the flight deck on a 777 without powering off the left AC bus.
You can use your knowledge of the Boeing 777 to shed light on what happened aboard MH-370, or you can use your knowledge of the aircraft to obfuscate the issue. Your choice.
But I suggest that you give some thought to what you are doing.