Now that is an interesting theory!
I always thought that Dina’s daughter was Osnat (who married Yosef).
Was I mistaken about that?
As to how Shimon could have married Dina: I once heard that Dina and Yosef were about the same age. Rachel was pregnant with Dina and Leah was pregnant with Yosef. During the pregnancy, Leah davened that her baby should be a girl, so Hashem made a “nes” and swiched the babies.
So Dina was partly Rachel’s daughter…therefore she was allowed to marry Shimon.
Did anyone else hear this?