You usually always want to animate the center of gravity by hand, as this is where a lot of the illusion of weight comes from.

In your case, you need to animate the root translation node, as well as the center of gravity to create a good look.

You application of the script looks cool though! You just need to find a way to be able to create some animation on top of the generated animation. Perhaps by having a locator, parented to another. The script run on the child, and you animation the parent. You then parent constrain the child locator to the center of gravity.

See if that works.