Huckabee would need someone to counter the perception that he is weak on Foreign Policy (which he is).
He needs someone young, with strong foreign policy credentials, and who will match up well against Barak Obama if he is Hillary Clinton's pick for veep.
Condoleezza Rice fits the bill. Rice would mop the floor with Obama in a debate.
Ron Paul wouldn't help Huckabee. Paul’s supporters would abandon him in droves for "selling out" if he joined the Huckabee ticket.