Dexter/Lumen. I think seeing where that could go would be interesting. I think, like Temis said, her hatred towards men in general would have been more intense and it would have eventually been directed towards Dexter. Plus, Dexter loved her--really loved her, perhaps even more than Rita--because Lumen knew who he really was. It would be nice to see Dexter truly be himself with her for a bit longer, especially when that's contrasted with his fake, social persona.