I don't think you can without making your own animation system.
What you can do however to make your life easier is to animate the legs using your animator and don't touch the bones in the top half of the body, then you can find child to all the bones in the top half and move them around at will with the other animations still going strong.
What you can do however to make your life easier is to animate the legs using your animator and don't touch the bones in the top half of the body, then you can find child to all the bones in the top half and move them around at will with the other animations still going strong.