I like the design of the version 3 but I have one question
Given that the MOSFET control pins will always be HIGH or LOW then the gate of th MOSFET can never float. This seems to make the 10k pull down resistor unnecessary. The only time the gate can float is if the Arduino fails.
Am I missing something
Once the Arduino is powered the gate on the mosfet should follow the Arduino pin and the pull down resistor is not required. However, while the Arduino is starting, or it is being reset, Arduino pins default to inputs until the sketch starts and the mosfet gate will be floating.