Lightbox

I have to honestly confess here that I haven’t read the entire content of the topic, but if with a little thinking you don’t give the team member element, but a color-section (or grid-row) an ID and give it the class mfp-hide, the color-section should be able to appear as similar in a lightbox.

if this is not enough – why don’t you open a page in a lightbox from your site.
Place that button and insert a manual link with the url of your wanted pages with addendum: ?iframe=true

see here https://webers-testseite.de/my-website/

PS: If it is an external page link – you must have allowed on that external link to be running in an iframe.
for that i allowed it via htaccess by: Header set X-Frame-Options "ALLOW-FROM https://webers-testseite.de/"

but on internal pages ( X-Frame-Options “sameorigin” ) this is not needed

i’m just participant as you – so no private content could be seen by me.
but maybe the edited tip will help you more than the inline-popup solution

see f.e. a portfolio masonry:
https://webers-testseite.de/portfolio-masonry/

i set the popup in child-theme functions.php to:
( that is just for that page-id on my code )

function add_modal_popup_einstellungen() { 
if(is_page(42989)){
?>
<script type="text/javascript">
window.addEventListener("DOMContentLoaded", function () { 
  (function($) {
    $('.av-masonry-entry').on('click', function(e){
      e.preventDefault();
    });
    $('.av-masonry-entry').magnificPopup({
      removalDelay: 700,
      type:'iframe',
      midClick: true,
    }); 
    $(document).on('click', '.popup-modal-dismiss', function (e) {  
      $.magnificPopup.close();
    });
  })(jQuery);
});
</script>
<?php 
}
}
add_action('wp_footer', 'add_modal_popup_einstellungen');

some css ( in this case the opacity is set to 0.97 that you can see it is a lightbox – if it is 1 – it’s nearby your example page from above.

#top.page-id-42989 .mfp-bg {
  background-color: #FFF;
  opacity: 0.97;
}

#top.page-id-42989 .mfp-iframe-scaler {
  width: 100%;
  height: 80vh;
  overflow: hidden;
}

#top.page-id-42989 .mfp-iframe-holder .mfp-close, 
#top.page-id-42989 .mfp-image-holder .mfp-close {
  color: #000;
}