I like this idea. In the absence of heavy med balls this could be an alternative, if done very carefully. However, dropping a kettlebell, or a dumbbell as the person above you suggested, involves a whole array of potential negative consequences. That's why medicine balls are so great for this--they're not going to break when you drop them, or break your floor, or you.
And like the other guy said, these will never be the cornerstone of anyone's program. They are different though, and present quite a challenge. They also teach balance and body control which are too often overlooked in training programs. Plus they are fun.