Suppose your brain were protected only by a set of bones with openings between them, like the ribs

Would this be satisfactory?

Thanks in advance!

Only if you don't mind a little thing called brain damage. The ribs work well because when they break, they typically don't pierce a lung or heart. Maybe a chest wall, but few people receive lifetime disabilities due to a rib that is broken and penetrates the chest cavity. However, the brain doesn't have a chest wall or any other protection. It also has no margin for error. With a broken rib, the chance that it would pierce through the heart is highly unlikely since there is so much non lethal areas to penetrate. The brain, however, would be damaged if even a small fracture found the bone being pushed into the brain cavity ie. the brain. Also there would be nothing to be gained. The ribs are the way they are because the chest needs to be able to move. The skull does not.

No... Too big a chance of them fracturing easily, like ribs. Then we would all have broken heads and be derp.