I thought I’d just add a response to highlight the features in TM. It’s not a direct answer to the “have you ever?” part of your question, but hopefully it helps chart a path for what might be possible.
The default pages are publicly accessible here: https://gitlab.artsman.com/_public/tmresponsivewebpages
There is also an online customizer that can help you generate a Bootstrap 3 theme for use with all of the pages: https://help.theatremanager.com/web-page-documentation/bootstrap-live-customizer
The customization works by overriding default pages with custom pages in your web page customization folder.
So, for example, if you wanted to customize 1/WebPagesEN/tmCheckoutConfirmation.html then you would start by referencing the default page, here, and then saving it into your local customization folder, and overriding/moving the parts that you’d like to change.
We also have some tips for finding the right web page to edit.