What you want to create its alrdy created, its called american staffordshire and even today there are individual dogs that are DA.
My dogs tolerates other dogs when im with him because he knows if he atacks i'll be very sad and i will have to yell at him, but be sure if the other dog, which i cant control,shows a little evidence of agression my dog is gonna be ready and ansious to grab his neck.
If you seen my movie you'll see my dog is a very friendly dog towards human, know or not known hes going to lick everyone because he was breed to be human non-agressive, but he was too breed to show aggresion towards others males and its just the instincts and genetics that own our dogs.
I like american staffordhsire and they way they are breed, just like bull terriers or staffordshire bull terrier, but i have an APBT and i must understand from where my dog comes and how i gotta deal with him.
Again sorry for my english