OP
I've thought of something like this for TSHTF scenarios. The best way I've come up with is putting it on the outside of the window and making a top support that you could roll up in the window, pinching it in place. The lower portion and middle would be supported by suction cups. (Yes I realize the suction cups are not the best support but it would mainly deter against thrown objects and would make it removable.)
For the rear side windows I am going to build bars across the window using 1" square tube and expanded sheet metal. It will double as protection in TSHTF scenario and for wheeling. I bet no has seen someone loose a rear side window while wheeling right?
For the rear, I don't have an answer, yet...
The Vehicle Gard stuff seems great but that's $500 that might stop a brick IF I install it right and IF it does what the company says it will. I KNOW that metal stops bricks.
Kurtis