I think since Gran Bahia Principe has an exclusivity agreement with Arrecife, the photographer would have to pretend to be a friend/family member. So you would need to book them a room for one night. This is also what a wedding planner in Houston told me they do all the time for destination weddings, because most hotels don't let you bring outside vendors. So the photographer masquerades as a friend or family member.
I am not lucky enough to have any photographer friends or family coming to the wedding, so I will use Arrecife. But I am very impressed with Arrecife's work that I've seen online and it seems that they know all the good spots to take the pictures and what poses look nice. I just have to save up money, because it's going to be expensive at $15 per photo!