At least for Subaru, the dcm also connects to all antenna so removing it disconnects gps antenna. For other cars, I'd still expect removing the dcm to be good enough for 95% of people given the current expectation from car companies that no one would want to remove the dcm.
If you log 32 bytes once per second that's only 962 MiB per year uncompressed. But 32 bytes is a lot (or depending on what you're logging not very much), once per second is almost certainly more frequent than necessary, and almost all vehicles spend the vast majority of their time turned off.
For example logging RPM every 100 ms, 8 bits gets you reasonable but not perfect accuracy and you're looking at 300 MiB per year of continuous operation. It's just not much of a storage requirement for quite detailed telemetry.
The reliability is way better than GitHub's uptime.
Better even than my car's uptime.
You must work in telco.
99.9999% or it's unusable :P