"the front and back reservoirs and pistons were totally independent of each other, the pedal would stop as soon as say, the rear flow stopped. Once hard in the rear, no flow would go to the front, hence no brakes up there."
The reason the rear port goes to the front brakes, they do the majority of the braking, and why discs where used up front. Any decrese of pressure its safer at the back. Everybody knows In the extreme panic stop, a car nose dives, effectively raising the rear almost to the point of no tire contact, with equal pressure, those brakes will lock. This happens with all tires the same size and big fat slicks, tires unload. Granted, center of balance has a lot to do with how the brakes are set up on each type of car. Low light car can be set equal to an extent, normal B-body, you better take some out of the rears and have more up front.