Think about that for a second. A single switch (i.e. single failure), that will shutoff both engines.
You really want to advocate that?
Not advocating so much as putting up for discussion. I suspect the certification authorities later decided against continuing the practice as it may raise more problems than it solves.
But it did take substantial g to trigger. There are a number of cars today that have a crash actuated fuel shutoff. I've had to reset one after a crash near my house.
One design has two metal balls on arms 90° apart that will close the valve on a sufficient frontal or side impact.
How the Viscount switch was done I don't know.