If we are going that far, I suggest hopping off just one station earlier at Crystal-lang.

Yep, I think Crystal is the thing that is making a real go at essentially this suggestion. And I think it's a great language and hope it will grow.

Do you know how Crystal compares with Haxe? That's another one that might fit the requirements nicely.

I don't understand the Haxe documentation but it seems to also have some kind of algebraic data type.

Maybe ReScript?