If you're placing a strong importance on ecosystem, and after something that can be used in a less-OOP / more functional style, it's hard to go past TypeScript (whatever distaste you may have for the dark corners of JavaScript).

A less vibrant ecosystem, but far stronger on the functional and string typing, take a look at OCaml (others have suggested good alternatives like F# or Scala if you want to leverage the existing VM-based ecosystems).