A wellbore select fire switch retaining member system and method with an integrated through wire and ground wire in a switch sub. The system/method includes a retaining member that has a form factor acceptable by a conventional switch sub. The retaining member incorporates an electrical connection to the center pin of a pressure switch. The system further includes a secondary piston aligned with a piston in the switch (switch piston) so that external pressure is fully acted upon the entire switch piston creating a reliable switch connection. Another system includes an integrated retaining member and switch module having a form factor compatible with existing switch subs. The integrated module inputs include a ground wire and a through wire and the outputs include a ground wire, through wire and an arming wire.