I think the bigger problem is A5. With A6, its a pain, but you could always solder a thin wire to the chip and run that wire out to a pin header glued to the side of the communication header. It's not an ideal solution, but I have done this before only with the Mega1280 to get access to one of the Timer inputs.
With A5, there is no way around it. It is shorted out to the NRD pin which means, unless there is a way to disable the NRD pin, you can't actually use the SMC controller as two of its output signals would short out.