make a child always have its own scale?

I found that just saying

 transform.localScale = transform.localScale;

in Update() worked like a charm. I guess it just needed reminding haha.

You can use this function whereever you are scaling the parent, it goes through the children and unparents them and then reparents them after scaling.

     private void ChangeParentScale(Transform parent,Vector3 scale)
     {
         List<Transform> children= new List<Transform>();
         foreach(Transform child in parent) {
             child.parent = null;
             children.Add(child);
         }
         parent.localScale = scale;
         foreach(Transform child in children) child.parent = parent;    
     }