I'm not convinced that this is the case. You can tell there was no real grand plan, but one thing I do think they did plan, was for Rey to be a something. Leading up to the force awakens, Abrams had said that the reason Rey, was just Rey, was a last name would give things away. They kept it secret because there was a plan for her, a big portion of the marketing revolved around who is Rey. It was Rian who decided the hardest thing for her would be for her to be a nobody. There is no debating that the biggest mistake that was made with Disney star wars, was no outline for the trilogy. But I firmly believe that Abrams had a plan for Rey that made her a somebody.