The ability to change themes based on what layout/page you are on can be quite ideal depending on the general layout of the page. I would love to see this in the application as right now it is something that we need and I can potentially see others wanting in the future as well.
Not sure how this could work as the theme CSS file is included in the index.html file of the application which is reused in all Angular pages.
I had noticed while looking for an alternative that there was this post: Humanistic and Software themes?
The gif seems to show the ability to switch the theme based on a drop down prompt.