There is a suggestion that the essence or spirit of Cylons and humans is the same. Indeed, in Buddhist thought one might consider conciousness a product of the universe and the level or quality of conciousness is coloured by its projection through the form it takes. This is orthogonal to your topic but something to consider in light of the Caprica prequel, the First Hybrid's comments, and the emerging end-game.

I can't make my mind up whether the Final Five are ancient or modern, or decide how much it matters. It's possible to speculate and spoilers suggest it may have some weight that Starbuck died and was remade in an artifical body, would be human in spirit and intent but Cylon in physical form, no be neither one nor the other. Again, it's huge speculation but the Final Five might have this type of quality about them.

The end game seems to be that neither human or Cylon can make that final step on the evolution ladder on their own but can do it if they work together. I'm not entirely convinced this was in Ron's original vision but his plan and audience comment seem to be creating something that squares the circle for both. I guess, in a funny sort of way that's a Final Irony to match the Final Cylon. Kinda neat, that.