Allow the use of a text link insted of a thumbnail

On my project, I do not want to have a thumbnail on which we can click to get the video playing (using colorbox).. I would like to have a simple link with a text like "movie" or "trailer" (with a play arrow before) and when you click on it, you get the colorbox video playing.
I have made a patch to allow this... this is not exactly a final patch, this is only a proof of concept (which is fully working)
This patch is adding a new formatter called: "Colorbox Modal with link" and allow the use of a custom text for the link (the play arrow is added in all cases)

Description of what I have done:
1)I have duplicated the colorbox formatter (PlugIn/Field/FieldFormatter/Colorbox.php) and called it ColorboxLink.php... By doing this my "patch" can work alongside with this module. All the changes reside in this file.

2)In function settingsForm I have added a radio button with 2 options "Use thumbnail or text" and a textarea to customize the link text: "Link text to use if no thumbnail"

$element['use_thumb'] = [
      '#title' => $this->t('Use thumbnail or text'), 
      '#type' => 'radios', 
      '#options' => [
        'thumb'=>t('Use thumbnail'), 
        'link'=>t('Use link')
      ],
      '#default_value' => $this->getSetting('use_thumb')
    ];
    $element['link_text'] = [
      '#title' => $this->t('Link text to use if no thumbnail'),
      '#type' => 'textarea',
      '#default_value' => $this->getSetting('link_text')
    ];

3) I have adapted the function defaultSettings as well as the function settingsSummary()

public static function defaultSettings() {
    return Thumbnail::defaultSettings() + Video::defaultSettings() + [
      'modal_max_width' => '854',
      'use_thumb'=>'thumb',
      'link_text'=>'trailer'
    ];
  }
 public function settingsSummary() {
    ...//changes start here
    $usethumb=($this->getSetting('use_thumb')=='thumb');
    $use=$usethumb?$this->t('Use thumbnail.'):t('Use link');
    $summary[] = $use;
    if (!$usethumb){
      $summary[]=$this->t('Text:').$this->getSetting('link_text');
    }
    return $summary;
  }

4) and finally, I have updated the function viewElements to show the text link:

 public function viewElements(FieldItemListInterface $items, $langcode) {
    $element = [];
    if ($this->getSetting('use_thumb')=='thumb'){
      $thumbnails = $this->thumbnailFormatter->viewElements($items, $langcode);
    }else{
     //Here is the new code
      $thumbnails =array( array(
        '#markup' => '<span class="glyphicon glyphicon-play-circle" aria-hidden="true"></span>&nbsp;'.$this->getSetting('link_text'),
      ));
    }
    ...

As you can see, I use a 2 classes to show a play arrow before the text: glyphicon glyphicon-play-circle This is working for my project because it is a bootstrap style which is used by my project.
Those class are defined like this in bootstrap:

@font-face {
  font-family: 'Glyphicons Halflings';
  src: url('../bootstrap/fonts/glyphicons-halflings-regular.eot');
  src: url('../bootstrap/fonts/glyphicons-halflings-regular.eot?#iefix') format('embedded-opentype'), url('../bootstrap/fonts/glyphicons-halflings-regular.woff2') format('woff2'), url('../bootstrap/fonts/glyphicons-halflings-regular.woff') format('woff'), url('../bootstrap/fonts/glyphicons-halflings-regular.ttf') format('truetype'), url('../bootstrap/fonts/glyphicons-halflings-regular.svg#glyphicons_halflingsregular') format('svg');
}
.glyphicon {
  position: relative;
  top: 1px;
  display: inline-block;
  font-family: 'Glyphicons Halflings';
  font-style: normal;
  font-weight: normal;
  line-height: 1;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.glyphicon-play-circle:before {
  content: "\e029";
}

Attached:
ColorboxLink.php: the new formater... if you don't want to use the patch, you can drop it into PlugIn/Field/FieldFormatter/
diff-ColorBox-vs-ColorBoxLink.patch: just for your info, the differences between Colorbox.php and ColorboxLink.php (do not use the patch)
video_embed_field-Allow_colorbox_on_Text-baud--8.x.patch: the "real" patch that will add the new formatter
New-ColorBoxLink-Formatter.png: some screen capt
=>In any case, you will need to add 2 css classes to show the play arrow before the text

I think that the best thing to do would be to merge ColorBox with ColorBoxLink: what do you think?