Appcelerator CLI plugin for Babel, allowing you to use ES6 inside of your Titanium apps today.
Run the following:
git clone firstname.lastname@example.org:dawsontoth/ti.babel.git ti config -a paths.hooks ti.babel/hooks
Add the following to any Titanium apps you want to use ES6 in:
<property name="ti.babel" type="bool">true</property>
Take care, I haven't tested this very much. Only use it on apps that you have backed up and under source control.