Okay, so let's talk crispy skin. It's one of the best parts of the turkey, right? But it gets eaten right away. I mean, it has a short window. You rip it off gingerly to avoid burning your fingertips, and you savor the crispy, flavorful crackle. Crispy skin does not make it to the leftover containers for that reason, and because it would no longer be crispy when reheated. So, roast your turkey in the oven (might I suggest this Crispy Skin Roast Turkey with Citrus Herb Brine), and cook this one out of the way in your crockpot.
This extra breast won't yield you any extra crisp skin, it will however give you extra ridiculously juicy and flavor-packed meat AND about two and half cups of gravy. Extra gravy is never a bad thing. Like, ever.