Well, first off there won't be any cables going to the inside of the car. The grill block will be fully automatic and all electronics will be under the hood. The current bench testing setup uses manual controls simply for testing purposes. Once things are ready to go on the car the manual control will be swapped for a temperature sensor that will control the opening and closing of the door.
Would it have been easier to do a manually actuated grill block? Absolutely!
This was a step for me to make me learn some electronics and how to work with micro controllers. Also, the Matrix is really my wife's car. She will not want to have to deal with opening and closing something and watching coolant temperature to make sure the engine doesn't overheat.
The actuator, while powerful won't be enough to mess up anything with the car. The door will be thoroughly tested before its installed as well to make sure everything will work correctly.