Custmizing the TinyMCE link/image popup in Plone 5.2

Plone Support Customizing Plone
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1

I'm currently trying to customize the TinyMCE link/image popup in Plone 5.2. I need to do things such as removing certain tabs, changing the start directory, and changing the list of favorites. I'm trying to do this by disabling the default plugins plonelink and ploneimage, and replace them with my custom plugins. I have gotten to the point where I can let a click on the "insert/edit image" button run the following piece of code:

require(
  [
    "jquery",
    "tinymce",
    "mockup-patterns-tinymce-url/js/links",
    "translate"
  ],
  function ($, tinymce, LinkModal, _t) {
    var $el = $("<div/>").insertAfter($(editor.selection.getNode()));
    var options = {
      linkTypes: ["image"],
      initialLinkType: "image",
      relatedItems: {
        selectableTypes: ["Image"]
      }
    };

    var imageModal = new LinkModal($el, options);
    imageModal.show();
  }
);

But this gives me the following error:

Uncaught TypeError: Cannot read property 'options' of undefined
    at e.init (plone-tinymce-compiled.min.js:1)
    at e.c [as constructor] (plone-base-compiled.js:3600)
    at new e (plone-base-compiled.js:3635)
    at plugin.js:29
    at Object.execCb (require.js:1696)
    at Module.check (require.js:883)
    at Module.enable (require.js:1176)
    at Module.init (require.js:788)
    at require.js:1460

From looking at the code of the TinyMCE-pattern (plone/staticresources/static/components/mockup/mockup/patterns/tinymce/pattern.js, methods addLinkClickes and addImageClicked), I think I have to access the pattern itself and especially the $el and options attributes, but I have no idea how to do this. Anyone know how? Or anyone know another (better?) way to customize the popup?