I would appreciate getting into more details. As it sounds like a made-up problem to me. Perhaps you don’t understand how simple it is to have a static website as compared to a dynamic one. Especially to some simple project.
Live Preview means, then, that you need to:
- have a web-based editor behind secure auth,
- create an environment resembling CI to rebuild the site on demand,
- trigger rebuilds when a user modifies the content stored on the server,
- make the new build available in a draft environment
- …where it doesn't affect the live site,
- …only grant access to collaborators,
- …without breaking assets, links in the pages, CORS, or CSP.
There are more constraints and pitfalls that I'm not going to enumerate here. My point is, this stops being simple as soon as you stop being hand wavy about it.