Question about polygon group

Crios

It's 'possible to add some Polygon Group to a finished character?

Let me give you an example, I have a character who has a bone that controls only the feet, but the same character has his fingers, and I would like to add an extra bone to control the fingers. To do this I first create a polygon group that includes the toes, excluding it from polygon group that covers the foot, and then add the bone.

Now it's possible do a thing without losing character morphs?