I actually got the idea of using a shield from the first picture in the OOC. My thoughts on how the shield works are something like this:
A shield in this setting definitely would get destroyed over the course of a mission. It would probably, however, absorb some damage, especially if it wasn't used all the time. It is not intended to be used every moment of the fight: actually staying behind real cover would be much safer, and avoiding shots altogether is better than trying to soak them. But it would have its uses.
For example, the shield could be used to provide some cover while you're running from one position to the next, or to shield a gap between two places so the other teammates can get by, or to provide some a buffer when you're at the rear of a retreat (hooking it onto your back and getting the heck outta there).
As to exactly how much it can soak, I figure "It's probably at least as effective as a layer of FRAME armor." Any given spot can take a few shots, and while really nasty anti-tank shots can most definitely pierce through it, it'll dull the impact that has on the FRAME itself.
That's my thoughts on the matter. I also think it makes a cheap, easy-to-produce option to bring to a fight, since it's literally just a big hunk of metal. I expect Max to have to get a new shield after most missions.
If this seems unreasonable, I'm okay with changing this, too. I didn't ask Aristo if the shield would be sensible, though I probably shield have.