I think that's a bit unfair as Elm is already seeing some professional use.

Though on the subject of inter-op, Purescript might be what you are looking for if you want a strongly-typed, Haskell-like language, compiled to JS with a less cumbersome foreign function interface.

Your point still stands though, I hope Elm comes up with some good ways to say "trust me I know what I am doing" and "here is some JS, run it".

EDIT: Though it might be that that goes against the whole premise of the language.