I have an old house with 3 bathrooms all on the same circuit. Each has a light with a receptacle above the sink controlled by a wall switch. (See image below.) I want to GFCI protect the entire circuit from the first bathroom switch in the circuit. There is 14/3 wire from that switch box to the light, so the switch feeds the light with the red wire. My question: how do I wire a GFCI/Switch combo to protect everything past it in the circuit, including the light fixture?