RE tailgate chips/damage from road debris. I expected to see damage from doing this on our old truck with TC, which we ran from L48 to AK and all around AK for a summer, as well as thousands of miles after that. Truck had good mudflaps. Tailgate had zero damage that I could attribute to being down. Sure it's possible to catch rocks and chip it up, but largely not a problem with mudflaps.
And those citing tailgate damage as a reason to not do this, have you ever looked at the lower panels on your vehicle? I'd start there, as the damage right behind the wheels is far worse than it would ever be on a tailgate.