I think the Cortex-R chips are more targeted here- I think the V8-R chips are designed specifically for automotive use, so I assume they have appropriate ratings.
I seen a few dashboard where there is an STM32 sitting connected to a single button, whose only duty is to register a key press, and burp something on the CanBus in response.
B) If you did have a $20 microcontroller for Canbus control of a window motor driver but it saved $19 in extra wiring/labor (driver controls usually route to all windows), provides reliable debounce, automated one-push-to-open, and allows things like holding keyless lock to close all windows, it's totally worth it.