well all molossers are more dominant then most dogs so you might have some problems there, but there are some breeds that "like" working together. so i would suggest that you look up the kangal, they can take the heat and are very good protection dogs. there's also a kind of Central asian ovcharka with a shorter coat that can handle the heat, they'r called alabai. i would not look into the long haired breeds with that kind of heat altough they would do anything to protect you, it is just not comfortable for them.
both these breeds are independant enough to work on their own.