If i was going to try to make mille fleur marans, I would start with plain black marans, not copper blacks, to keep the genetics as simple and free of other modifiers as possible. I am NOT a genetics whiz with chickens, but in two generationss I would think you would be able to get at the very least, mottling on your birds, and another generation or two you could be showing some brown based birds with some mottling. As for your egg color during that time, it would probably be straight in the toilet, but you would have several generations to try to bring it back to at least a four.