Could point the src of the script tags to a server-side script to invoke the parser or maybe a web server module that catches the <script type=”application/javascript”> and runs the content of the tag through the parser.

As for the lambda syntax I think the best is from C# e.g. function(x){return x > 0;} would be… x => x > 0; with multiple arguments and lines being…

(x, y) => { 
  if(x > 0) {
    return 'X greater than 0';
  }
  else if(y > 0) {
    return 'Y greater than 0';
  }
}

var sales =

;

JavaScript parsing engines are inconsistent enough (e.g trailing commas in object literals) at base level. You’d need a pretty good reason to tackle it; like creating something that is radically different to JavaScript, not just JavaScript with some extra weirdness.

It would be much nicer as an extension though.