Since there's no way to add a new language to the editor and this feature can't be implemented via plugins and definetely there's any workaround with the current version of WeBuilder: please add CoffeeScript language support.
Even if WeBuilder can't compile the code into JavaScript, this job can be done with a plugin BUT when you open a CoffeeScript file using the Javascript's syntax the editor throw errors, so basically you can't use WeBuilder as a CoffeeScript editor at the moment.
I'm working in a SASS compiler plugin, there's one to compile LESS, so the CoffeScript support makes WeBuilder a very atractive and complete deal.