Proposed EEDT API.php

<?php

//Instead of using ee_debug_toolbar_modify_output as the primary mechanism of adding content to the toolbar,
//we add an additional extension hook for adding content

class Eedt_memory_history_ext {
 
 /**
  * Method called for adding toolbar panels
  * @param $view Eedt_view
  **/
  public function ee_debug_toolbar_add_panel($view){
    
    $view->setName('memory_history');
    $view->setButtonTitle('Memory History');
    $view->setButtonIcon('something.jpg');
    $view->setOutput(/* HTML View output */);
    $view->addJs('script.js');
    $view->addCss('styles.css');
    
    //Adding an ajax calleable method
    $view->addAjaxMethod('Eedt_memory_history_ext', 'ajaxData');
    
    return $view;
  }
  
  //This function will recieve calls for data from JS
  function ajaxData($params){
   
  }
  
}

//EEDT View Class
class Eedt_view {
  
  //Toolbar button icon
  function setName(){}
  
  //Toolbar Button Name
  function setButtonTitle(){}
  
  //Toolbar button icon
  function setButtonTitle(){}
  
  //Panel HTML
  function setOutput(){}
  
  //Panel JS
  function addJs(){}
  
  //Panel CSS
  function addCss(){}
  
  //Where to inject the HTML
  //By default this is going to be in the panel area,
  //But this could allow people to inject content before and after the
  //toolbar
  function setInjectionPoint(/* before, panel, after */){}
  
  //Disable/enable toolbar button (in case they are doing something crazy 
  //with the above method and a button is not needed)
  function setButtonDisplay(/*Bool*/)
}