I'm pretty sure the third/fourth pins are used for communication to the battery. I doubt the phone would be happy it wasn't responding. I vaguely remember some phones can just use a resistor for that pin? Either way it's not quite that simple.

Maybe. Try it and see. If it doesn't work it's probably just a temperature sensor (thermistor) and a resistor indeed simulates a certain temperature the same way your power supply simulates a charge state.