There is something like this already in place. It's hard to notice most of the time, but when brick damage is on, smaller bricks are easier to destroy than larger bricks. Baseplates (being the largest) are impossible to kill typically.
The main problem is that most weapons which have the ability to destroy more than a couple of bricks usually use an area damage effect which does usually mean taking out a large portion of a building.
For now, you can use wrenchevents to make a brick(s) disapear when hit with a projectile.