Most any of the little, low pressure pumps will push fuel to the mechanical pump, no real need to remove it. Also, most of little pumps you can draw fuel right through them so the mechanical pump can still function the way it was intended to. Just use the little pump to get the carb full and help with starting via a push button switch.
The idea behind the oil pressure switch is purely safety. If you in a wreck and get knocked out, the pump will only run as long as the engine has oil pressure. The original three wire Chevy Vega switches turned pump on above 3 psi oil pressure, the other lead turned pump on when started was engaged, third feed was power source.
