I love Riot (you know that), I love ECMAScript 6 (2015) (you know that), but I don't like "transpilation" (you know that). And I prefer to work with Traceur than Babel (to my mind, in-browser transpilation of Traceur is better). See how to do this
I love Riot, and to my mind it's useful that we don't need to pre-compile tags. But you have to do that if you want work with ECMAScript 6 or Coffeescript. That'a pity, because, these transpilers can make in-browser transpilation.