4. The "Main-Board" Will Wear Out
For something like this to work, it would require very hardy electricals, as constantly replacing the parts in the circuit would wear the circuit out. The advantage of this system would be that the mainboard would be easily replaceable, however the point still stands that the parts would wear out far quicker than a normal phone's electrics, purely by being used for what they are used for. I'm not even going to bring up how easy it would be to be playing around, showing off your awesome new gadget and then oops...there goes the camera.