Yes!
I am doing this in MDL-52954 (work in progress) for Moodle 3.1.
There is much left to do in that issue - but the editor parts are working perfectly.
It doesn't use mustache templates directly - instead it uses a new "fragments" loader (also only in 3.1).
https://tracker.moodle.org/browse/MDL-53056 and MDL-52715 are the fragments issues.
General developer forum
Rendering HTML editor in Mustache client-side
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