Still, I don' think people would mind if they were static.
If they were, brake calipers and disks would constantly clip inside the wheels due to the small gap during turns, and especially bumps/jumps/etc. Also it will look weird.
You could also make it so the calipers are modeled to the body but not the brake disc, so the disc still moves up and down, I don't know.
Calipers are pretty much mounted onto the brake disc.
Pretty much the only way of doing this is modeling fully functional suspension. I did a quick search on the forums and apparently there is a way to do that, so I'll tinker with it a bit later.
