Correct me if I am wrong, but if you set all bones not to deform you will always discard all deformations. So doing this repetitive doesn't make sense, since you will always delete deformations that you made just a second ago. Or I missed something?
ttomorrow I'm not quite sure what you mean. The point of disabling the deform setting is for that bone to be ignored by the vertex weighting process. In a complex rig like this one, some bones are responsible for moving the character model while others serve as utility or "mechanism" bones, where they assist the function of the deformation bones but don't directly deform the model.