Maybe block chance should be 110% effective for obstacles the target is taking cover in, and 125% if crouching? E.g. a crate has a 40% chance to be hit if the target is not near it, 44% if next to it and standing, 50% if next to and crouching. Would make a little sense.
A final "hunker down" stance could be neat, but adds complexity for only a little more depth.
I also would prefer some smoke that deals a little more or armopiercing/DoT damage so you do more interesting stuff than just throwing it on the most exposed soldier.