This was a pretty biased article really, bit of Boeing bashing going on. Pretty ironic really as this confusion would not exist on a Boeing product. Its a bit hard to miss a pilot holding the yoke to his/her groin.
A few dollars per aircraft. The actual cost of creating a workaround for this problem. Mobile phone vibrator motors. These things are simply tiny motors with an off balance crank to create the rumble and could be easily mounted in the stick. The rumble becomes active when the flight control system is receiving control input from multiple devices. Simple and tactile. Also audible, but a workaround not a solution.