This is a well reasoned and eloquently argued theory, and while it would make for an interesting plot twist, I think it will ultimately be proven false. The lightsaber Rey presents to Luke was in Obi Wan’s possession for a time, and it was the first lightsaber Luke ever handled, but it did not belong to either of them. A Jedi constructs his (or her) own lightsaber. What Rey has there was produced by the late Anakin Skywalker prior to his corruption to the Dark Side. If it calls to Rey as a result of some bloodline connection, she can’t possibly be a Kenobi.