I put a RX switch on a plane once inside the model then put a small aluminum tube that went out both sides of the fuselage. The tube is long enough to go up against the switch in the off or on postion. There are two tubes one on each side of the switch.

to turn on the plane stick a small wire (2-56 pushrod for example) thru the tube on the port side of the fuselage and push the switch on. to turn off the plane push a wire thru the tube on the starboard side and push the switch in the off position.

the only thing exposed is a a very small hole in the side of the port and starboard side of the fuselage.