I am not making it sound easy, for I am not developer.
If you read what I said above, you will notice that I said this: "if adding another player would result in a poor framerate or poor graphics, then I will understand the devs."
I doubt it's about framerate or graphics. Anyway let's see what happens.
Maybe it is. Fable 2 will not feature 2 dogs in coop mode because of framerate issues, as Peter Molyneux himself said.