In the podcast for A Disquiet Follows My Soul, RDM explains why he retconed Nicky’s paternity. He didn’t want to have another hylon running around, felling that Hera should keep her place in the show’s mythology. Nicky would mess all that up.
This drastically reduces the likelihood that Kara is Daniel’s daughter, as cool as that may be. It’s not impossible as Starbuck also inhabits some sort of special place in the show, unlike Nicky who was just Tyrol and Cally’s kid. But being special doesn’t necessitate being part Cylon. She may be part god or just a bad-sorry-Barb human.