Another thought experiement on broccoli v1 changes to more easily hook into and/or compose inputNodes

my-plugin-2.js

function MyPlugin(inputNodes, options) {
  this.options = options;
  
  // In this example, let's say we need to do something special with the first
  // inputNode as compared to the others.
  [this.firstNode, ...this.otherNodes] = inputNodes;

  this.firstNode.appendChildNode(this.options.startCallback);  // pre-firstNode hook
  this.wrapChildNode(0, this.options.secondCallback);          // post-firstNode hook

  // Callback after every "otherNode"
  this.otherNodes.forEach((n, i) => this.wrapChildNode(i + 1, this.options.postEachOtherCallback));

  // Make `finalCallback` only get called after _all_ input nodes are fully finished
  // using the little eventComposeHelper util (included below). A bit superficial
  // but illustates needing to "hook" into the completion of X different nodes
  this.appendChildNode(this.options.finalCallback);

  Plugin.call(inputNodes, options);
}

MyPlugin.prototype.build = function() {
  // Whatever else this plugin wants to do in its build ...
}