The physics behaviour is meant to mimic real life physics in a 2D environment.
A bigger object (one with a bigger collision polygon) behaves different from a smaller one. Also when you have a vase, for instance, its point of gravity won't be at the neck.
Changing these settings would take away the point of physics.
If you want a limited form of physics and not have it behave "realistically" it would probably be better to write your own custom movement. I've done it before and it gives you a lot more influence as a programmer.
I told my dentist I had trouble with my teeth and asked her to fix it without looking in my mouth..