Yes, they would be good on a farm. As for sleeping outdoors that is okay, as long as that is what he or she wants. If they act like they want to be in with you, as mine does, definitely let them sleep inside.
We have a Bernese,a cat who he sleeps with in our garage, a mini donkey who the dog absolutely loves. While I am taking care of my chores my Bernese sits outside the pasture and cleans the donkeys face and sits with him until I come from barn. I think a Bernese is a wonderful farm dog.