In general I think this is an interesting idea, but I feel like this has a lot of overlap with asm.js and WebAssembly. With this standard we would have standar

In general I think this is an interesting idea, but I feel like this has a lot of overlap with asm.js and WebAssembly. With this standard we would have standard dynamic JavaScript as the world knows it today, a restricted subset ('constraint spec') that is still designed for human readability/writability, and then asm.js/WebAssembly, which would not be written directly but instead would be an output of code written in other languages. Programmers will want interoperability between all of these paths, and that is a lot of complexity for these engines to manage.