Change object's center of mass

It would be nice if it was possible to change where an object’s [0, 0, 0] position is located. A current workaround is to simply add an empty group and position it where you want it to be the central point and set the object’s position relative to that group. Imagine you have the zapbot, I’d like to be able to set its center of mass on its feet or head, or whatever, so where I choose would be the [0, 0, 0].