A way to upload old html pages with all its assets via WordPress admin and to add a fixed menu on top of those (a la Wayback Machine)

Inside a WordPress website I manage at a custom hosting, I want to have a few joke websites that looks like personal Geocities pages from the 90s, with animated gifs and all. Generally I edit these pages at a text editor manually and upload them with all the associated assets in their own folders, completely outside of the WP ecosystem. The problem is that I’m having big trouble by adding anything outside the core WP folders in the hosting I’m using for some reason. I don’t think it is a problem specific to WordPress (the hosting is new and has some very aggressive security measures), but regardless that issue, I was also thinking to figure some way that:

  • I can upload all the html pages, its images and all INSIDE the WordPress admin (including having some chance to replace these very html pages if I want to update its content or such, even if I have to re-upload a new html page locally rather than edit it inside WP), and
  • A way via WP itself that adds some fixed frame at the top or the bottom of all uploaded html pages, merely with the main site name and some button to go back to the main page, not unlike the fixed navigation that appears at the top on old webpages on the Wayback Machine on Archive.org (that site is not built on WordPress, but you get the idea).

It’s short of embedding a website inside a regular WP post type while being also able to edit these inside WP at will, but I don’t know if there’s a clean way to to it. At the moment I only have a few html pages that are independent of each other, but eventually I would want to have a full old fashioned website and I would need that all the links inside these works and to not upload twice any resources each html page has.