A club would be cool, a place where they play random Destiny soundtracks, or maybe a soundtrack specifically made for the club. Maybe it could be an Easter Egg in the tower instead of a place you to walk to? Like you have to walk through a noclipped wall or press a secret button to get into it. It'd give a cool pizazz to the Tower. As for a casino, I don't see why not? Lots of MMOs have minigames where you can rack up more currency. I wouldn't mind trying my luck.