Makes sense. I was thinking if there could be a bootable fuzzer of this kind, but you're right that it would be very difficult for it to be both usable and not crash very quickly.
Secondly, one could trivially log "I am going to try this" to a file, go ahead and do it, and if the machine crashes you consult the log and read exactly what was about to be done and evidently caused a hang. You don't necessarily need to write a log entry after doing something, in this case you can deterministically log what you are about to do and make deductions therefrom.
I've been using this with HP ProLiant servers and (for me, at least) it has always worked as intended.
For more info, search "linux watchdog timer".