I'm sorry guys, but I have lost all direction on this story. I didn't plan it out well enough, so I lost traction and I have completely fell off the wagon. I will be marking this story as complete, even though it isn't an never will be. I am sorry.
However! Here is what would have happened!
They would have been attacked by an akuma during the wedding. It would turn out to be Chloe, who was never able to reclaim her popularity after Marinette showed everyone how terrible she was in highschool. This high profile wedding was supposed to be hers. Then Adrien and Marinette would have finished the wedding and it would have ended with Adrien kissing his beautiful bride.