I highly doubt a v2 switch will be released. It doesn’t have anything to do with interfacing with sensors, but rather tells the robot when to switch into driver and autonomous modes.
On the Vex website it shows CA$25.99 - do you really have to pay that much tax?https://www.vexrobotics.com/276-2335.html
However, I don’t think that you need one to run auton. I don’t have a controller with me right now, but if you press ‘Timed Run’ or ‘Competition’ instead of ‘Run’ when you have selected a program on V5, I’m pretty sure it will do the auton without a switch. (The program does have to be formatted in a competition template)
About going straight - during driver control, it is generally much easier to just correct the turning by hand with the controller. In auton however, some correction in code is often needed. The best way of doing this is using a PID algorithm. There are many resources and threads already out there about this.
Here’s a recent example: