Hi, if you like the idea of Wasm sandboxing you might be interested in what we are working on: BrowserPod :-)
https://labs.leaningtech.com/blog/browserpod-beta-announceme...
https://labs.leaningtech.com/blog/browserpod-beta-announceme...
The main issue that I see with Browserpod is very similar to Emscripten: it's designed to work mainly in the browser, and not outside.
In my view, where Wasm really shines, is for enabling containers that work seamlessly in any of this environments: browsers, servers, or even embedded in apps :)