Sure, it should be possible. You could have the head use a Sprite node with a SpriteSheet, an AnimatedSprite, or some other form of animation, while still having the rest of the body use bone-based animation. You just want to make the head you are animating a child of the head bone, and if you need to position anything, to use their local transforms/rotations rather than global ones.
Moving the torso is a little harder, depending on what you are meaning. You could have the legs use a frame-by-frame animation and connect that to the spine, in basically the same way as the spine. It should be doable, though the IK may have a slightly harder time reacting to changes in the position of the legs, but you could just manually offset the bones as needed to adjust.
