I fitted an extra starter button on my truck when the ignition switch started getting flakey after 25 years. But you have to be careful where you put it so a passenger doesn't press it while the engine is running. Tends to make quite a bit of noise and isn't good for the teeth on the flywheel.
As to the key on the steering column, I suspect it is due to the mandated steering lock to deter theft. But any crook with a screwdriver can break it in a matter of seconds. Citroen had the best idea. Park the car and the wheels retracted leaving it sitting on the frame. But they were so ugly, what thief in his right mind would steal one?