Here’s another idea: an option to enable “card readability checks”.
Every so often when the buffer is flushed and the card idle, read back the first few blocks from the most recent images written to the card. Potentially check many images in case the card has a large RAM buffer: we want to read from the flash cells.
The idea is to detect a failed card as soon as possible. I’m skeptical that a failed card will be a “silent failure” while shooting but maybe so, especially with cheap cards, and the sooner a failure is detected the better.
In future cameras that support 90 MB/s cards perhaps the camera could compute a checksum of each file as it is written and write the checksums to the card too. When the buffer/card is idle whole files and checksums could be read back and verified, all in the name of telling the photographer ASAP that something is wrong.
This is expensive in battery life to do, but a lot of people seem paranoid about card failures, and it only has to happen once to be a very expensive failure…