Look into American Bulldogs they look almost exactly like a pit, I have a buddy with one and its a smart dog. It would make a good protector. Don't know how its hunting instincts are but I'm sure you can train them to though. This dog does have a natural retrieving instinct and will chase a ball all day long. Good nose on them also.
I don't think many people would try to break into a house if there's a lab inside thats trained to bark at noises. My brother has a yellow and when the pizza man knocks on the door he usually decides to wait half way down the sidewalk.
The desire for peace and the simplistic and misplaced guilt many people have, create a tendency to make everyone who demands a standard of behavior into some kind of Neanderthal.