The idea/spirit of this code works but, in actuality, it does not work when you first click page > add new and switch to a new template. This is because, the fields are not there as soon as you fire the .on change (it takes a second).
When that .on change event tries to append the #postdivrich, the message placholder has not yet been lazy loaded onto the page. See what I mean?
The trigger needs to happen _after_ the acf field group is loaded onto the page — NOT after the #page_template select changes.
BTW, my first crack at this was almost exactly the same code you just posted. This is why I suggested making it a feature. What we really need access to is code that fires after the fields are loaded.
