We would be open to supporting TinyMCE as a third-party add-on... particularly as we ramp up the features available in TinyMCE Cloud over the next 1-2 years.
Of course, we aren't Moodle experts so would need some help in doing this.
Doing this work needs to be balanced against other priorities, so any indications that it would be something your institution would consider - please ping me or contact our team via https://www.tinymce.com