For easy theming, I suggest you to take a look at the Classless Project, which will be super easy to integrate to in your case and will bring many already made themes with it -- and much more to come.
The ursprung[2] micro CMS is integrating Classless with success to this day.
The only thing I'd suggest is, use ES6 instead of CoffeeScript or provide an ES5 copy of the code.
The CoffeeScript code you see is for the bookmarklet used on the playground. It is old code, coded in a rush, most for proof-of-concept. I'm slowly rethinking this playground and theme development stuff, so this is going to be replaced.