I understand that a minor revision is planned for the Duet2 series. If it hasn't been asked for yet, I would like to request some sort of protection on the fan outputs to prevent idiots like me from blowing the output mosfet's.
We looked into providing fan output short-circuit protection some time ago. Unfortunately, thermal fuses are too slow to provide protection. Electronic fuses for 12V circuits are readily available, but not for 24V circuits.
A related question - is the Duet3 more idiot proof? If so that would be a big bonus for me.
Yes it's more idiot-proof, for example against shorting the external +3.3V or +5V rails to a higher voltage. The fan mosfets have a higher surge current rating; however they will still fail if you short a 24V fan output. They may survive shorting a 12V fan output, but I haven't tested it.