Need To Be Able To Do More With Static Pages

I'm about to use ZipApp for a Student Event and it would be great if things weren't so restrictive when using Static Pages. I would like to be able to add my own HTML/CSS/JavaScript code to them, but doing so in the 'Content' area when creating a page converts characters to UTF, and modifying the static-XXXXX.js page has no effect.

I've also tried using an iFrame and had no success.

Would it be possible to allow users to upload an HTML or JavaScript file and set that as a Static Page?