Flexible materials are not a suitable substitute for hooks or other rigid structures. Materials such as rope will tighten around the piercing, causing the skin to be pulled to one point and rip. More rigid items such as hooks are definitely better choices unless the goal is to tear free (for example in a ball dance or Sundance-type ceremony).In addition, doing this would result in major contamination of the rigging system, on top of the fact that there isn't really any way to sterilize rope. Stick to hooks!