This would annoy me as a user, I don't care that you really want the await/async feature. ES5 is not that bad. It's not like the difference between Lua and Vimscript. Just use ES5 or compile your ES6 prior to distributing.
To be fair you could (and I have...) say the same thing about coffee script.
Just let the plugin authors write in whatever-the-heck they want and compile it to js, and distribute as js, like everyone else.
On the bright side, this shows that the github guys are thinking about things other than coffee script at last. Thank goodness.
The summary is, It Just Works™, efficiently.
too bad its taking so long, i cant wait until full support comes to browsers