I think I get your point, and while I haven't done much with meteor since a few weeks after it was first announce, I recently started a couple react.js projects using jspm. I'm not sure, yet, if jspm is ready for prime-time, but getting started was as simple as:

    npm install [-g] jspm 
    jspm init
    jspm install react

For es6/es7, adjust config.js babelOptions.

I've nothing to add in regards to ios / android / desktop, but for getting up-and-running, jspm seems to do the job quite well.