Looks like you are not using hierarchies properly. You can set "transform width/height" for all children in a hierarchy. Then when you change the scale of the parent object, all children will be scaled automatically with it.
You also don't need to link parts of the hierarchy with instance variables. If collider_char is the parent object, to pick its head you simply use "collider_char Pick Children Head" condition.
You can create a family called Limbs for all arms/legs sprites. Then the code may look like this:
if Body Scale=0.5
Body pick children Limbs : Limbs set scale to 0.7