I know the official wireless shield (xbee) is connected to the first port of ATmega328P (PD[0..1]). This is the same port where is connected the ATmega16 for USB connection.Obiouvsly, if we want communicate to the xbee and send data to the pc at the same time we can't.
eg. 0-ohm resistors
I don't understand your second answer. I'm talking about solder jumpers (or similar) to get Arduino board more flexibile. At least with official shields.