I think I've worked it out. The Final Cylon is...
He's the only major character missing from the
Last Supper picture, and he says 'Christ' in an
episode of Season 3 - there is no Jesus in the
polytheistic religions of the Colonies. D'anna's
'forgive me' comment in Rapture might be in
relation to Cottle's actions regarding Hera,
the Cylon-Human baby. Pretending it was dead,
and so on. D'anna was especially worked up
about the little brat.
Also from a recent email:
Me: I wonder what [Roger] Corman could make with $200 million.
Jeff: easy. 20,000 movies.