Don't wanna disrupt your thinking, thinking process, but there's no way a goose could scare away a coon or any predator, except maybe a hawk, like Lydia said. They can sound the alarm for larger predators, but sometimes they are afraid and simply stay quiet. Even my chickens have been that...
I don't see why you can't free range your geese and not lock them up at night. They handle any kind of weather just fine. Mine spend the night on the pond if they feel threatened. I did lose 4 in the first few years I had them in GA, but the 2 ganders I have left are quite vigilant. By the way...
Ha! This is funny that a Rottie doesn't like water. My 3 1/2 YO Female dives into our pool continuously until we make her stop. She is also a house dog as she came from a city home where the kid would just open the door and let her run. It's a problem we haven't been able to correct in 2 1/2...