Given there is no support for modules yet with projections it would help a lot to update the version of V8 bundled.
From what I can tell currently its using 3.17.11 which came out over 2.5 years ago. Lots of builtin js functionality (map,forEach,string manipulation,etc) has come out since then that would dramatic reduced the code and mostly likely improve performance of projections. Plus tools like Browserify and Babel could be used fully without resorting to polyfills.