Have you looked into doing just that? There are a number of options and more arriving all the time.

https://ghost.org/docs/api/v2/gatsby/

https://ghost.org/docs/api/v2/eleventy/

https://ghost.org/integrations/netlify/

It feels a bit overkill to pay $29 per month just for a hosted blog UI. And if you're running Ghost yourself on a server or on your computer, it's not really a static site anymore.

From the OP:

> Of course I'd like a static website for deploying, but I'd love a web gui which acts as a frontend for such generators.

If you want such a gui on your local machine you're not much more than a few commands away

  npm i -g ghost-cli
  ghost install local

This looks promising. I'll check it out.