I have a GFCI receptacle installed on the side of my house in a weatherproof box. It is on a dedicated circuit. I need another receptacle on the other side of the wall in the car port so my wife can charge her Prius. I don't want to run another circuit but I also don't want both receptacles on the same circuit because at some point they will both get used and trip the breaker (or become a fire hazard). So I'd like to install the new one and add a three-way switch on the hot side to switch between the hot feeds on the receptacles. Then only one can be in use at a time. See illustration below. The top is two receptacles in parallel and the bottom is two receptacles switched. The switch and 1st receptacle would be in a double gang weatherproof in the carport and the 2nd would be outside on the side of the house.
Does anyone see a problem with doing this? Is there anything in the code which prohibits it? Any advice is appreciated.