Hi! I am also getting married in Jamaica and having the same issue with the photographer. I do believe that Grand Lido does allow photographers and outside vendors. My travel agent told me about the charge at Couples and also informed me that Sandals does not allow outside vendors.
We really want to get married in Negril so we were looking into Moondance villas, Grand Lido, Riu Tropical Bay, and The Caves. They all allow photographers.
Hope that helps! In the forum there is a section dedicated just to Jamaica and there is a lot of info on different resorts that might help as well.
Good Luck!