The CMS didn't support any kind of HTML/JS embed, and had quite a short character limit per "Text" block. But luckily, that block didn't filter out _all_ inline HTML - only some characters.
So, a bootstrap "Loading" element was inserted, along with a script tag which would bring in the rest of the resources and insert those in to the page where the bootstrap was placed. This quickly became a versatile, re-usable loader, and allowed us to launch the features. But all this grew from a very inelegant hack which just happened to work.