Driving MFET with IO Expander ( mcp23008/mcp23017)
It should work assuming the pcb layout is done correctly. The gate only draws current when turning on or off. Assuming you’re not expecting to do pwm, then I don’t forsee an issue.
The pulldown resistors can be 10k. How did you come up with 4.6k? They are only to ensure the mosfet remains off during reset/until the expanders are initialised.
A 22R’gate stopper’ resistor in series with the gates is suggested.
Yes, you will need level shifting on I2C.
Driving the mosfets with 5V is preferred.
Have you considered using something like a TPIC6B595?