Support Swiper Element (web components)?

That's a good point and, in fact, first steps towards that are already there. If you fetch 2.0.x-dev version you will see package.json there (as well as the new option for "Source" of the swiper, "Package". If you

npm install
npm run build

And have selected Package for Swiper template in question you will see it's working. What is weird however, Element is not really recognized, because for quite a while I am busy with Ckeditor5 implementation of Swiper here (from time to time when I catch some time :) and for that, all goes really perfect when using as element inside CKEditor5 scope. Once it is saved as such markup in drupal and later viewed on page, it simply does not work, even though <swiper> and children would still have all required classes.

Long story short, there's a bit more here to do but is coming as more broad solution. And thanks for pointing indeed!