For the majority of people, they can just use airplane mode and disable the scanning feature (that’s the one you are referring to I guess).
If you do not trust Google, I recommend you don’t use Android. A hardware switch to turn of radios is just a hack around that. It can work, Librem is following that route.
You could construct a faraday cage as well. You could surround a FP2 with aluminium foil, though not the screen.
The majority of people are not this paranoid though. Which is why there’s no market for this device.
You can create demand, yes, but that requires effort. It doesn’t come magically for free.
Kickstarter projects need a market (demand); else they fail. You can gauge interest with a Kickstarter project, but it takes time and effort; therefore money. If the volume is too low, the R&D for the project won’t see ROI. So, yes, you do need a market. I am not going to discuss this specific argument further with you, btw.
It is the same with Spotify. You don’t like Spotify, that’s fair enough. But for the vast majority of people, vinyl or buying CDs or ripping these or even downloading MP3s is just too much hassle. And for people who are privacy oriented and who want to avoid Bluetooth and WiFi tracking, airplane mode is then sufficient.
Failing SD cards? Get an industrial grade SD card. These fail far less. They do cost more as well, though, but the option is available for you right now, including for the FP2. Example: (ATP, via Digikey).
Dual microSD is a terrible way to backup. If you lose your device (stolen, lost, damaged) then you lose your backup! You should keep your backup offsite, not with the device, and ideally encrypted.
Your idea is not really new, btw. See e.g. Hardware switch for microphone and cameras to improve privacy