The plan for analog outputs is the following:
A 64-step digital pot, connected to a variable low LDO regulator rated at 5 amps. It would take up 3 digital outputs and 1 analog input for feedback.
the next stage would be PWM capable of 30 amps or better
also, check that car - my car uses a resistorpack for the blower motor, but the vent doors are all cable-actuated, so I'd have to retrofit servos.