To kill VA straight away with a parameter is trivial. You can even do it yourself by executing a command externally which contains an inline function
I have to point out here that shutting down VoiceAttack in such a manner will trigger the "VoiceAttack Improper Shutdown" message at startup with most implementations; I have tried:
Environment.Exit(0);
As a C# inline function; Displays the message.
Close 'VoiceAttack' process
As a VoiceAttack action inside a command; Displays the message.
Application.Exit();
As a C# inline function; This actually causes VoiceAttack to freeze after "Unloading plugins", though it doesn't display the warning afterwards despite having to kill it.
Application.OpenForms["frmMain"].Close();
As a C# inline function; Does not display the message.
Close window 'VoiceAttack'
As a VoiceAttack action inside a command; Does not display the message.
However, the latter two are reliant on the "Minimize to system tray" option being disabled, presumably as otherwise the window/form handle won't exist.
I've thought about requesting an "Exit" action built-in to VoiceAttack, which would gracefully shut it down without triggering the warning, but deemed it too niche.