6. The Colonists make robots as well, which resemble the original Kobol models. It's probably reasonable to assume that someone who had a hand in designing the first batch also has a hand in designing this new batch, since "our" toasters look similar to the 2000-year-old toasters they found on Earth.
You're forgetting a couple of key details.
The Cylon rebels gave the Centurions free will. Baltar planted the seeds of dissent by pointing out that there's a definite pecking order among the Cylons on the baseship, and the Centurions are low on that pole.
So, it stands to reason that the Cylon Civil War...skinjobs vs. skinjobs, may well become skinjobs vs. mechanicals at some point now that the Centurions have free will.
If that's true,then it could well be a case of mechanicals vs. skinjobs on Earth. Indeed if what happened before happened again, then the skinjobs on Earth are equivalent to humans on the colonies, so it would therefore be their mechanicals that rose up against them.