The problem of Cain’s wife is one of the oldest exegetical challenges in the Bible, and more to the point it is one which has taxed expositors over the centuries far more than other problems. The reason for this is that Genesis 1 has traditionally been understood as teaching that Adam and Eve and their immediate family were the only humans alive at the time. This is a natural reading from the text alone.
But the fact is that a natural reading of Genesis 1:26-4:2 (that Adam and Eve and their two sons were the only humans in existence), actually conflicts with a natural reading of Genesis 4:14, 17, that humans outside the primal family already existed, that Cain was aware of them, and that he left the primal family to go and marry one of these other people, leaving the covenant community. So we have two natural readings and they conflict with each other. What are we to do?
Traditionally, Jewish and Christian exegetes simply privileged one passage over the other; they chose to privilege the “Adam and Eve and their two sons were the only people who existed” passages in Genesis 1:26-4:2 over the “other people already existed” passages in Genesis 4:14, 17. We should recognise this as a flawed strategy. When we privilege one passage over another, we are not actually harmonizing the text, we are simply attempting to avoid a conflict by devaluing one of the two conflicting passages so that it is silenced. In effect, we break Scripture.
When faced with two natural readings which conflict when we read the text alone, how can we avoid privileging one over the other? Well, we have learned the hard way (from incidents such as the Galileo affair), that reading the text alone, uninformed by external sources, can lead to exegetical error. In this case a host of external knowledge informs us; paleology, geology, archaeology, biology, and other sciences tell us that Genesis 4:14, 17 is correct, that there were other people around, and that they did not come from Adam and Eve.
Ironically now we know that this is a fact, we don’t have a conflict with Genesis 1:26-4:3; the passages can be harmonized because it’s easier to explain how people were not mentioned in Genesis 1:26-4:3, than to explain that they didn’t exist even though they are mentioned in Genesis 4:14, 17.
With that as the backdrop to your question, I’ll look into what you have suggested and return tomorrow with more information.