I would focus on functional languages. They don't change much nor often and guarantee (in 99% cases) everything is going to work reliably as soon as it builds successfully. The less people you have the more you need functional languages. Elm, Elixir, F#, Scala, Clojure, Kotlin etc.
As for Haskell - I omitted it intentionally. It seems beautiful yet not practical enough. Perhaps it is perfectly practical but I didn't have a chance to learn it to the level on which in starts feeling this way.
