Yeah, Podrick Payne has a part to play most certainly. He is an innocent bystander right now. He has done nothing to give offence to the BwB. It is for that reason that Brienne desires to save him. One he is a young man. Second, he's innocent. The next Brienne/Jaime chapters are going to be quite interesting though. Why have Pod interact with Tyrion, then Brienne, and then Cat? He had plenty of chances to be killed off. He keeps popping his little head up now and again. I don't think that would be the case if he were to just be executed by Lady Stoneheart.