Fusion local.css not taken into account

Mimemail does not pick up the file css/local.css in Fusion. This file is used to override styles so it's quite a big deal to not include it when the theme has been customized.

I don't know much about drupal/php/theming but it seems there could be some inspiration to be taken from ckeditor.module code:

    // add custom stylesheet if configured
    // lets hope it exists but we'll leave that to the site admin
    $css_files = array();
    switch ($conf['css_mode']) {
      case 'theme':
        global $language, $theme_info, $base_theme_info;

        if (!empty($theme_info->stylesheets)) {
          $editorcss = "\"";
          foreach ($base_theme_info as $base) { // Grab stylesheets from base theme
            if (!empty($base->stylesheets)) { // may be empty when the base theme reference in the info file is invalid
              foreach ($base->stylesheets as $type => $stylesheets) {
                if ($type != "print") {
                  foreach ($stylesheets as $name => $path) {
                    if (file_exists($path)) {
                      $css_files[$name] = $host . $path;
                      // Grab rtl stylesheets ( will get rtl css files when thay are named with suffix "-rtl.css" (ex: fusion baased themes) )
                      if (defined('LANGUAGE_RTL') && $language->direction == LANGUAGE_RTL && substr($path,0,-8) != "-rtl.css") {
                        $rtl_path = substr($path,0,-4)."-rtl.css";
                        if (file_exists($rtl_path)) {
                          $css_files[$name."-rtl"] = $host . $rtl_path;
                        }
                      }
                    }
                  }
                }
              }
            }
          }
          if (!empty($theme_info->stylesheets)) { // Grab stylesheets from current theme
            foreach ($theme_info->stylesheets as $type => $stylesheets) {
              if ($type != "print") {
                foreach ($stylesheets as $name => $path) {
                  if (file_exists($path)) {
                    $css_files[$name] = $host . $path;
                    // Grab rtl stylesheets ( will get rtl css files when thay are named with suffix "-rtl.css" (ex: fusion baased themes) )
                    if (defined('LANGUAGE_RTL') && $language->direction == LANGUAGE_RTL && substr($path,0,-8) != "-rtl.css") {
                      $rtl_path = substr($path,0,-4)."-rtl.css";
                      if (file_exists($rtl_path)) {
                        $css_files[$name."-rtl"] = $host . $rtl_path;
                      }
                    }
                  }
                  elseif (!empty($css_files[$name])) {
                    unset($css_files[$name]);
                  }
                }
              }
            }
          }
          // Grab stylesheets local.css and local-rtl.css if they exist (fusion based themes)
          if (file_exists($themepath . 'css/local.css')) {
            $css_files[] = $host . $themepath . 'css/local.css';
          }
          if (defined('LANGUAGE_RTL') && $language->direction == LANGUAGE_RTL && file_exists($themepath . 'css/local-rtl.css')) {
            $css_files[] = $host . $themepath . 'css/local-rtl.css';
          }
          
          // Grab stylesheets from color module
          $color_paths = variable_get('color_'. $theme .'_stylesheets', array());
          if (defined('LANGUAGE_RTL') && $language->direction == LANGUAGE_RTL) {
            if (!empty($color_paths[1])) {
              $css_files[] = $host . $color_paths[1];
            }
          }
          elseif (!empty($color_paths[0])) {
            $css_files[] = $host . $color_paths[0];
          }
        }
        else {
          if (file_exists($themepath .'style.css')) {
            $css_files[] = $host . $themepath .'style.css';
          }
        }
        $css_files[] = $module_full_path ."/ckeditor.css";
        break;

      case 'self':
        if (file_exists($module_drupal_path .'/ckeditor.css')) {
          $css_files[] = $module_full_path .'/ckeditor.css';
        }
        foreach (explode(',', $conf['css_path']) as $css_path) {
          $css_path = trim(str_replace("%h%t", "%t", $css_path));
          $css_files[] = str_replace(array('%h', '%t'), array($host, $host . $themepath), $css_path);
        }
        break;

      case 'none':
        if (file_exists($module_drupal_path .'/ckeditor.css')) {
          $css_files[] = $module_full_path .'/ckeditor.css';
        }
        $css_files[] = $editor_path .'/contents.css';
        break;
    }

The above code contains ckeditor's patch found in #818378: Not all css files are loaded.
With that patch ckeditor also uses Fusion css/local.css for styling text in the editor.
Is there a quick fix I could apply to mimemail until a proper solution is found?