Not a bad idea at all, but just one question: if Syd disapeared for two years after their trip, and her memory all the way back to the night she shot francie was erased some how, then when she first asked Vaughn about Will and Francie he would have reacted differently (like very confused b/c he would figure she would remember that), or at least ask what the last thing she remembered was. And certainly, if she had asked about a wedding ring that she gave to him, he would have burst into tears on the spot or something.
It seems pretty obvious to me that the night of her disapearance was the same night of the fight