Actually, I can see the cloak having some practical applications. It would conceal her costume, when she was trying to be inconspicuous. It would give her an extra layer of padding, especially for when she was out on her motorbike. It would make it easier to carry weapons and gear, if she needed them. And it would keep her warm on those cold Gotham nights when the insulation provided by a single layer of silk netting wasn't cutting it. But you're certainly right about the risk of getting Dollar Bill'd.