I tested mine with the naza soft ware because I did still have the phantom when I was checking them. and is how I even noticed the first time that my S2 was bad. Then i still checked it with a multi meter set to do a continuity test(in other words has a connection) on the switches contacts. My meter has a buzzer in it. So when its got a straight short between both test probs it buzzes. if no connection it don't buzz.
While I agree with a lot of what you are saying, the quoted part above is easy to test without a the bird. You can connect your controller to the RC assistant standalone and test your switches at any time. If they are failing I would expect you could see this in the assistant.
That totally slipped my mind that you can use the rc assistant to check the switches without the phantom hooked to the naza soft ware. But if you do have the phantom the naza is easier being you don't have to open up the controller to plug it in to the usb. But in either one would show the same if the switch is not working at all or if its just starting to fail and touching it or wiggling it at all in any of the 3 positions on each switch shows it changing in the software. or if not going to what ever mode each position is supped to be. would show its bad. and best to catch that before flying rather then after losing the phantom being finding out after don't help any one other then maybe just give them so closer on the cause of death.