Shock tower Braces
this is not a GM design... suspensions are designed a certain way... each part has a purpose... excluding t bar cars (front end springs act differently under cornering) the springs, front or rear are only to keep the car at ride height and to keep the car from bottoming out on a bump
a sway bar is designed to keep the body level thru a corner... therfore you need the correct spring rate for the vehical and the correct sway bar for the weight and handling desire of the vehicle...
now where t bars can act a little different is that they will slightly act as a sway bar, thats why the solo racing bars are 1.04+ in diameter...
Not to be contradictory, but I believe when he said "GM Design", he was referring to GM's tendency to use lighter springs and larger sway bars to improve ride quality and gain better handling.
As for the rest of your statements regarding suspension and handling theory, I believe you may have mistated a few points or maybe I am not reading it right.
Of paticular interest is your comment on torsion bars. Could you elaborate as to how a higher rate torsion bar would be any different from a coil spring of a higher static rate but similar installed height or wheel rate?
For More Understeer* For More Oversteer**
Chassis Feature Adjust As Indicated Adjust As Indicated
Front Tire Pressure Lower Higher
Rear Tire Pressure Higher Lower
Front Tire Section Smaller Larger
Rear Tire Section Larger Smaller
Front Wheel Camber More Positive More Negative
Rear Wheel Camber More Negative More Positive
Front Springs Stiffer Softer
Rear Springs Softer Stiffer
Front Anti-Roll Bar Thicker Thinner
Rear Anti-Roll Bar Thinner Thicker
Front Roll Center Higher Lower
Rear Roll Center Lower Higher
Weight Distribution More Forward More Rearward
Kind of a mucked up chart. But you can see how spring rates and sway bar rates work in conjunction with each other. Also, all springs act the same. It's the design of the suspension that determines how that energy is used.