Too easy a present system to bypass. Even a cheap mityvac would allow you to build enough vacuum to shut down. Or a tiny electric vacuum pump motor/pump as the shutoff does not consume vacuum.

You would only activate it when wanting to shut down. I have heard of some people just sucking on the vacuum line extended into the reach of the driver.

Mechanically putting the lever on the injection pump into shutoff mode is another way that would work well. Either by cable or electric solenoid.