Why not use a language that has the benefits of TS + everything you say and is designed to be independent from JS.

I'm thinking of OCaml for example. Why not use OCaml rather than TS?

Edit: Actually the idea is so obvious that you have ReasonML that can compile both to JS and assembly and is basically OCaml with a JS-like syntax: https://reasonml.github.io/docs/en/what-and-why

Isn't that exactly what you're thinking of?