Further fail-safeing option....
In addition to the RFID "open the door" provisions, you could add a little panel with four switches, outside the house. All would me momentary (like a doorbell). Two would be normally open, two would be normally closed. You could make one of them your doorbell, too... even if it took using a DPST switch there.
They would be wired into the circuit to the electromechanical strikeplate... entirely "dumbly"... they wouldn't be "seen" by the Arduino at all. But you would wire them up so that the strikeplate would only work if one (or maybe you'd do it so that all were required) of the right buttons ARE pressed, and none of the wrong buttons are NOT pressed.