Tyrol might want to put Nick in super-max daycare before Cally gets wind of this. She is not stable. I sense another neck-snap.
If it turns out they are "cylons", it doesn't necessarily mean the are automatically evil or that they haven't been through genuine emotional struggle these past years. I don't think anyone besides Helo and Baltar have come to terms with that.
I can kinda see Tigh as a cylon. I mean, you can't just plop in a group of 5 essential new characters without some sort of gravitas or charisma to hold them down. At least 1 of the 5 had to be someone high up in the series. (Adama, Roslin, Tigh, Baltar, Zarek kind of people)