Turns out to be quite arduous:

- You ask for reasonable support for both object-oriented and functional programming, this already contradicts with the notion of state (that objects suppose to contain in OOP) and "stateless" ways of FP, let's ignore that for a moment

- FP means different things for different people - some would argue it has to have well thought type system, but what exactly that means? Is strongly but dynamically typed like in Clojure is okay (with added sugar like Clojure.spec)? Or it has to have static types? Does it have to have then type inference like in Elm? Or definitely it has to have algebraic data types like in Haskell? Or maybe dependent types like in Idris?

- Concurrency models vary too, for example: STM in Clojure and Haskell aren't exactly the same. Actor model in Erlang is a beast and sounds awesome on paper, but in real life process coordination may become a headache. Primitives based on CSP model are also known to have their own quirks. Concurrency in any language is never simple and straightforward.

- You're asking for an fast FP language - with immutable data structures and lazy/non-strict evaluation it's probably unrealistic to get it to run as fast as native code

- And "simple to learn" is also very subjective quality - for some Python is easy, but Clojure is hard. For some Haskell is not that difficult as people describe it. For some it feels like insurmountable mountain.

As you can see - it's not that simple. And we probably not gonna get a "perfect" language that suits everyone anytime soon.