The schematics for the current Pinebooks are available. It should be the same for the Pinebook Pro once it's released.
There hasn't been any indication that a kill switch will be available for the Pinebook Pro or that there has been any interest of one thus far.
The WiFi/Bluetooth module is part of the mainboard on the Pinebook Pro as seen on the image at the bottom of this post:
https://forum.pine64.org/showthread.php?tid=7093 . That's at the top left of the main board.
I guess you could short the power to ground for the module or completely desolder the module. I would go for the first option as it would be easier to reverse if something goes wrong.
If this seems like an approach you would pursue, I would advise you to spend some time getting to know the schematics and how the circuitry actually works before attempting any of this. Louis Rossmann has multiple great videos and live streams demonstrating repairs on Macbooks and this playlist here which is intended for novices to get to know the hardware side of things:
https://www.youtube.com/playlist?list=PL...tiZqUTH7GT
Of course, there is the option of not loading the drivers without doing any hardware mods though it seems you have different requirements. Or maybe just disconnecting the antenna wire will be enough to degrade the signal to an acceptable level.
It may look a bit daunting at first but given what you strive to achieve, it should be worth it to spend a couple of days researching. It won't be hard to disable the module on the hardware side. But doing it in a safe, controlled and reversible manner would require some effort.
It's a nice idea to request a hardware switch for the wireless module. Or exposed contacts to make this mod very easy. Perhaps a goal for the next iteration?
PS: Maybe someone who is active on the IRC channels or Discord already disabled the module by accident or can help you to identify how to short the module safely. It's a good idea to check them.